Digital VTR for recording special replay data with appended error correction codes

ABSTRACT

Data separating means extracts intra-frame or intra-field encoded blocks from an intra-frame or intra-field encoded, and inter-frame or inter-field encoded digital video signal, and a digital audio signal contained in an input bit stream. Error correction code appending means appends error correction codes to the extracted intra-encoded blocks. Recording means records the data having the error correction code appended, in special replay data recording areas predefined on the magnetic recording tape. During fast replay or slow replay, error correction is achieved even for the replay signal with a low output level and a poor symbol rate.

BACKGROUND OF THE INVENTION

The present invention relates to a digital video tape recorder(hereinafter referred to as digital VTR) having a track format forrecording digital video and audio signals in predetermined areas onoblique tracks, and relates to a digital VTR in which the digital videoand audio signals are input in the form of a bit stream, and the bitstream is magnetically recorded and played back.

FIG. 93 is a diagram showing a track pattern of a conventional, generalconsumer digital VTR. Referring to the drawing, a plurality of tracksare formed on a magnetic tape 10, in a head scanning direction inclinedto the tape transport direction, and digital video and audio signals arerecorded therein. Each track is divided into two areas, a video area 12for recording a digital video signal and an audio area 14 for recordinga digital audio signal.

Two methods are available for recording video and audio signals on avideo tape for such a consumer digital VTR. In one of the methods,analog video and audio signals are input, and recorded, using a videoand audio high-efficiency encoding means; this is called a basebandrecording method. In the other method, the bit stream having beendigitally transmitted; this method is called a transparent recordingmethod.

For the system of recording ATV (advanced television) signals, now underconsideration in the United States, the latter transparent recordingmethod is suitable. This is because the ATV signal is digitallycompressed signals, and does not require a high-efficiency encodingmeans or a decoding means, and because there is not degradation in thepicture quality due to transmission.

The transparent recording system however is associated with a problem inthe picture quality in a special playback mode, such as a fast playbackmode, a still mode and a slow mode. In particular, when a rotary headscans the tape obliquely to record a bit stream, almost no image isplayback at the time of fast playback, if not specific measure is taken.

An improvement for the picture quality for the transparent recordingsystem recording the ATV signal is described in an article Yanagihara,et al, "A Recording Method of ATV data on a Consumer Digital VCR", inInternational Workshop on HDTV, 93, Oct. 26 to 28, 1993, Ottawa, Canada,Proceedings, Vol. II. This proposal is now explained.

In one basic specification of a prototype consumer digital VTR, in SD(standard definition) mode, when the recording rate of the digital videosignal is 25 Mbps, and the field frequency is 60 Hz, two rotary headsare used for recording a digital video signal of one frame, beingdivided into video areas on 10 tracks. If the data rate of the ATVsignal is 17 to 18 Mbps, transparent recording of the ATV signal ispossible with the recording rate in this SD mode.

FIG. 94A and FIG. 94B show tracks formed in a magnetic tape using aconventional digital VTR. FIG. 94A is a diagram showing scanning tracesof the rotary heads during normal playback. FIG. 94B shows scanningtraces of the rotary heads during fast playback. In the example underconsideration, the rotary heads are provided in opposition, 180° spacedapart on a rotary drum, and the magnetic tape is wrapped around over180°. In the drawing, adjacent tracks on the tape 10 are scanned by tworotary heads A and B having different azimuth angles, alternately andobliquely, to record digital data. In normal playback, the transportspeed of the tape 10 is identical to that during recording, so that theheads trace along the recorded tracks. During fast playback, the tapespeed is different, so that the heads A and B traces the magnetic tape10 crossing several tracks. The arrow in FIG. 94B indicates a scanningtrace by a head A at the time of five-time fast feeding. The width ofarrow represents the width of the region read by the head. Fractions ofdigital data recorded on tracks having an identical azimuth angle areplayed back from regions meshed in the drawings, within five tracks onthe magnetic tape 10.

The bit stream of the ATV signal is according to the standard of theMPEG2. In this bit stream according to the MPEG2, only the intra-frameor intra-field encoded data of the video signal, i.e., the data of intraencoded block (intra encoded block) alone can be decoded independently,without reference to data of other frame or field. Where the bit streamis recorded in turn on the respective tracks, the recorded data arereplayed intermittently from the tracks during fast replay, and theimage must be reconstructed from only the intra-encoded blocks containedin the replay data. Accordingly, the video area updated on the screen isnot continuous, and only the fractions of data of intra coded block arereplayed, and may be scattered over the screen. The bit stream isvariable-length encoded, so that it is not ensured that all the replaydata over the screen is periodically updated, and the replay data ofcertain parts of the video area may not be updated for a long time. As aresult, this type of bit stream recording system does not provide asufficient picture quality during fast replay in order to be accepted asa recording method for a consumer digital VTR.

FIG. 95 is a block configuration diagram showing an example of recordingsystem in a conventional digital VTR. Referring to the drawing,reference numeral 16 denotes an input terminal for the bit stream, 18denotes an output terminal for the bit stream, 20 denotes an HP dataformat circuit, 22 denotes a variable-length decoder, 24 denotes acounter, 26 denotes data extractor, and 28 denotes an EOB (end of block)appending circuit.

To improve the quality of fast replay pictures, the video area on eachtrack is divided into two types of areas. That is, the video area oneach track is divided into main areas 30 for recording the bit stream ofthe ATV signal, and copy areas for recording important part of the bitstream which are used for reconstruction of the image in fast replay.Only the intra-encoded blocks are effective during fast replay, so thatthey are recorded in the copy areas. To reduce the data further, onlythe low-frequency components are extracted from all the intra-encodedblocks, and recorded as HP (high priority) data.

The bit stream of MPEG2 is input via the input terminal 16, and outputvia the output terminal 18, without modification, and sequentiallyrecorded in the main areas 30 on each track of the tape. The bit streamfrom the input terminal 16 is also input to the variable-length decoder22, and the syntax of the bit stream of the MPEG2 is analyzed, and theintra-picture data is detected, and timing signals are generated by thecounter 24, and the low-frequency components of all the blocks in theintra-picture data are extracted at the data extractor 26. Furthermore,EOBs are appended at the EOB appending circuit 28, and HP data isconstructed at an HP data format circuit, not shown. The HP data isincorporated in the recording data for one track, and recorded in thecopy areas 32.

FIG. 96A and FIG. 96B show an example of replay system in a conventionaldigital VTR. FIG. 96A schematically shows normal replay. FIG. 96Bschematically shows fast replay.

Separation of data from the magnetic tape during normal replay and fastreplay are performed respectively in the following ways. During normalreplay, all the bit stream recorded in the main areas 30 is replayed,and the bit stream from the data separation means 34 is sent as thenormal replay data, to an MPEG2 decoder, provided outside the replaysystem. The HP data from the copy areas 32 are discarded. During fastreplay, only the HP data from the copy areas 32 are collected, and sent,as fast replay data, to the decoder. At the data separation means 34,the bit stream from the main areas 30 is discarded.

A method of fast replay from a track in which main areas 30 and copyareas 32 is next described. FIG. 97A shows a scanning trace of a head.FIG. 97B shows track regions from which the replay is possible. When thetape speed is an integer multiple of the normal playback speed, ifphase-locking control is conducted by an ATF (automatic track following)method or the like for tracking by moving the head itself, the headscanning is in a predetermined phase relationship with tracks having anidentical azimuth. As a result, the data replayed by the head A from thetracks recorded alternately by the heads A and B, are fixed to thosefrom the meshed regions.

In FIG. 97B, if the signal having an output level larger than -6 dB isreplayed by the heads, the data is replayed by one head from the meshedtape regions. The drawing shows an example of nine-time speed replay. Ifreplay of the signals from the meshed regions is ensured at thenine-time replay, the regions are used as copy areas, and the HP dataare recorded in the copy areas, so that the reading of the HP data fromthese regions at this speed is possible. However, reading of thesesignals at different speeds is not ensured. Accordingly, a plurality ofareas need to be selected for the copy areas, so that the replay signalscan be read at different tape speeds.

FIG. 98 shows regions where the copy areas overlap for a plurality ofdifferent replay speeds. It shows examples of scan regions for threedifferent tape speeds, for cases where the head is in synchronism withan identical-azimuth track. The scan regions where the reading by thehead is possible at different tape speeds overlap, at some of theregions. By selecting the regions at which the overlapping occurs as thecopy areas, reading of the HP data at different tape speeds can beensured. The drawings show the regions at which overlapping occurs atthe fast-forward at four-time, nine-time, and 17-time speed. Theses scanregions are identical to those of feed-forward at -2-time, -7-time and-15-time high speeds (i.e., rewind at 2-time, 7-time and 15-timespeeds).

Even though there are overlapping regions for different tape speeds, itis not possible to determine a recording pattern so that identicalregions are always traced at different speeds. This is because thenumber of tracks crossed by the head differs depending on the tapespeed. Moreover, it is necessary for the head to be capable of startingtracing at whichever identical-azimuth track. For this reason, identicalHP data is repeatedly recorded over a plurality of tracks, to solve theabove problem.

FIG. 99 shows examples of scanning traces of the rotary head atdifferent tape speeds. Regions 1, 2 and 3 are selected from among theoverlapping regions for five-time and nine-time speeds. If identical HPdata are repeatedly recorded over 9 tracks, the HP data can be read ateither of five-time and nine-time speeds.

FIG. 100A and FIG. 100B show scanning traces at five-time speed replay.In the illustrated example, identical HP data is repeatedly recordedover five consecutive tracks. As will be seen from the drawings,identical HP data is recorded over the number of tracks identical to thenumber of times of the tape speed (i.e., 5). In either of case 1 andcase 2, either the head A or B can read HP data from correspondingazimuth track. Accordingly, providing the copy areas in each track, in anumber identical to the number of times of the tape speed at the fastreplay, and repeatedly recording the HP data there, the copied HP datacan be read at various speeds, and in either the forward or reversedirection.

In the manner described, the special replay data is recorded in the copyareas, repeatedly, to improve the picture quality during the specialreplay in the transparent recording system.

FIG. 101 shows a recording format on a track in a conventional digitalVTR. Main areas and copy areas are provided in one track. In a consumerdigital VTR, a video area in each track has 135 sync blocks (SB), and 97sync blocks are assigned to main areas and 32 sync blocks are assignedto copy areas. The sync blocks at the regions corresponding to the 4-,9- and 17-time speed shown in FIG. 98 are selected for the copy areas.The data rate of the main areas is about 17.46 Mbps (97×75×5×10×30), andthe data rate of the copy areas where identical data is repeated 17times is about 338.8 kbps (32×75×8×10×30/17).

FIG. 102A and FIG. 102B show an example of the configuration of a trackcontaining video and audio data.

The magnetic tape of a digital VTR according to the specification(hereinafter referred to as SD specification) defined by the SD mode, avideo area of 149 SB and an audio area of 14 SB are provided on bothsides of a gap, as shown in FIG. 93, and the video and audio data arerecorded in these areas, together with error correction codes. Employedas the error correction codes for the video areas in the SDspecification are (85, 77, 9) code (hereinafter referred to as C1 checkcode) in the recording direction (right-left direction in the drawing),and (149, 138, 12) Reed-Solomon code (hereinafter referred to as C2check code) in the vertical direction. Employed as the error correctioncodes for the audio areas are (85, 77, 9) Reed-Solomon code (C1 checkcode) in the recording direction, like the video signal, and (14, 9, 6)Reed-Solomon code (hereinafter referred to as C3 check) in the verticaldirection. Auxiliary data (VAUX data) is recorded in front of and at theback of the video data.

FIG. 103 shows an example of configuration of one sync block on themagnetic tape. As illustrated, the region of 1 SB is formed of 90 bytes,and a header consisting of sync pattern recording region 36 of twobytes, and ID signal region 38 of three bytes are formed at the headend, and recording region 42 for the error correction code (C1 checkcode, in the example illustrated) of 8 bytes is provided at the back ofthe data region 40 of 77 bytes. In FIG. 102A and FIG. 102B, the headerparts are omitted.

Because the conventional VTR is configured as described above, andspecial replay data is repeatedly recorded in the copy areas, therecording rate for the special replay data is very low. In particular,the quality of the reconstructed pictures formed during slow replay orfast replay is low.

For instance, if the intra-frame is formed twice a second, the amount ofdata of intra-encoded blocks of the ATV signal is predicted to be about3 Mbps. In the prior art, only 340 kbps can be recorded, and the qualityof the reproduced picture is very degraded.

Moreover, the data for the respective fast replay speeds is recorded,being dispersed over a wide region. Accordingly, if the track isnon-linear, it is difficult to achieve accurate tracking control overthe entire data region, and the replay signal from some of the regionsmay not be of a sufficient level.

Furthermore, during special replay (fast replay, slow replay, stillreplay and the like), the rotary head crosses a plurality of recordingtracks obliquely to pick up the replay data intermittently, as wasdescribed above. It is therefore not possible to form error correctionblock (video data) shown in FIG. 102A and FIG. 102B from the replay dataduring special replay. That is, during special replay, the errorcorrection using C2 or C3 check code is not performed, but errorcorrection using C1 check code alone is applied to the replay data.

If the error correction using the C1 check code alone is applied, if thesymbol error rate 0.01, the error detection probability is 1.56×10⁻³.This means one error per about 8 sync blocks is detected. Because thereplay data output is not stable during special replay, so that thesymbol error rate can often be more than 0.01. Moreover, the recordingdata is variable-length encoded, so that when an error is present, thesucceeding replay data cannot be used, leading to degradation in thepicture quality. The rate of undetected errors is also about 7.00×10⁻⁸.Thus, the frequency of occurrence of undetected errors is high.

Moreover, during fast replay, the data rate is low, and only thelow-frequency components are replayed, so that the resolution of thepicture is poor.

Furthermore, it is necessary to pick up data for a plurality of fastreplay regions in one scanning of the head during fast replay, so thatwhen the track is non-linear, or when the scanning trace is non-linear,the data at the fast replay region where the non-linearity is presentcannot be reproduced.

Moreover, since it is necessary to pick up data for a plurality of fastreplay regions by one scanning of the head, replay can be performed onlyat certain speeds. The speed at which replay can be performed islimited, and the number of the replay speeds is small.

Moreover, the rotary speed of the drum of the four-head configuration ishalf that of the drum of two-head configuration, so that the angle withwhich the head scanning trace crosses the track is larger, and thereplay with the four-head configuration drum from the fast replay regionis possible only at a speed half the speed at which the replay withtwo-head configuration drum is possible from the same fast replayregion.

Furthermore, when the level of the replay signal fluctuates, the syncbit and the succeeding ID bits, and the first parity are reproducible,and the succeeding digital data is reproducible only up to its middle,and the rest cannot be reproduced because of the decrease in the levelof the replay signal. In such a situation, the errors in the digitaldata is not detected until the result of the check using the secondparity is produced. It is therefore necessary to conduct the predefinedcalculation for performing the check, and time is spent before the errordetection.

Moreover, the amplitude of the replay signal varies periodically becausethe head crosses the recording tracks, so that burst errors frequentlyoccur, and this cannot be detected easily nor quickly.

Moreover, the data used for fast replay is formed by extracting part ofthe data of the packets transparent-recorded, so that the length of datafor forming a block of image is shorted. For this reason, when recordingis made for the region used for transparent recording, disposing sync,ID, header, and packets in a predefined format, the fast replay signalcannot be recorded using the same format. The recording signal formatforming means is therefore complicated.

Moreover, the fast replay data is used in common for all the replayspeeds, so that the period at which one screen of image data isreproduced and displayed during fast replay at each speed is determinedby the time for which the region in the tape longitudinal direction inwhich one screen for fast replay is recorded. Accordingly, the time forwhich one screen of image data is reproduced is inversely proportionalto the speed. With higher speed, the picture changes quickly, while withlower speed, the picture changes slowly. As a result, the displayedimage is easy to see for the viewer.

Furthermore, the region used for recording fast replay signal is limitedto the region where reproduction is possible commonly for a plurality offast replay speeds. Accordingly, the number of sync blocks for recordingthe fast replay signal is limited to the head scanning traces at thetime of highest-speed replay, and the amount of data which can berecorded is small.

Moreover, when considering the fluctuation in the position of the headscanning trace due to fluctuation in the tape transport speed or thedrum rotary speed, the region from which the data is reproduced withoutfail during fast replay is further reduced. This is particularlyproblematical in connection with fast replay with a higher speed.

SUMMARY OF THE INVENTION

The invention has been achieved to solve the problems described above,and its object is to provide a digital VTR with which the picturequality is higher in special replay, such as slow replay, still replayand fast replay.

Another object is to improve the resolution during fast replay.

A further object of the invention is to provide a digital VTR with whicha fast replay signal can be reproduced without fail even when the trackis non-linear or the scanning trace is non-linear, and which isreliable.

A further object of the invention is to provide a digital VTR with whicha fast replay is possible at a large number of speeds, and which isconvenient to use.

A further object of the invention is to provide a digital VTR with whicha fast replay is possible at the same speed without regardless ofwhether the drum is of two-head configuration or four-headconfiguration.

A further object of the invention is to provide a digital VTR whichpermits detection of burst errors at a short processing time using ameans of a simple configuration, and detection of erroneous correction.

A further object of the invention is to enable use of a common recordingformat for the normal data and the fast replay data, and to therebysimplify the format forming means in the recording system and the ID andheader reading means in the replay system.

A further object of the invention is to provide a digital VTR with whicha fast replay is possible at a plurality of speeds, and the screen isswitched at an interval to provide pictures which are easy to see.

A further object of the invention is to provide a device which canrecord and replay a maximum amount of fast replay signal at each of thefast replay speeds.

A further object of the invention is to provide a device capable ofreplaying the fast replay signal without being affected by thefluctuation in the head scanning traces.

A further object of the invention is to provide a device capable of fastreplay at a very high speed.

According to one aspect of the invention, there is provided a digitalVTR for recording recording data having digital video and audio signals,with error correction codes respectively appended in the recording andvertical directions, in respective predetermined areas on oblique tracksof a magnetic recording tape in a predetermined track format, andreplaying from the areas, comprising:

data separating means for extracting data of intra encoded blocks in theform of intra-frame or intra-field blocks from the intra-frame orintra-field encoded, or inter-frame or inter-field encoded digital videosignal, and the digital audio signal, contained in an input bit stream;

error correction code appending means for appending error correctioncode to the data of the intra-encoded blocks extracted by said dataseparating means; and

recording means for recording the data with the error correction codeappended, in the recording areas allocated in the magnetic recordingtape to special replay data.

With the above arrangement, when replay signal obtained intermittentlyby scanning the magnetic recording tape during fast replay or slowreplay is used to form a replay picture, it is possible to achieve errorcorrection, and accordingly, even for the replay signal having a lowoutput level and a poor symbol error rate, a special replay picture of asatisfactory quality can be formed by applying error correction.

It may so arranged that the recording means disposes the special replaydata recording areas in such recording areas that by scanning themagnetic recording tape once with a rotary head at a predeterminedreplay speed during replay of the special replay data, said errorcorrection code can be reconstructed.

With the above arrangement, the capacity of the memory required in theerror correction decoder for forming an error correction block can bereduced. Moreover, the timings for control over writing and reading ofthe replay data into or from the memory, and starting the errorcorrection can be synchronized with the rotation of the rotary head, sothat the control over the memory and control over the error correctiondecoder can be simplified, and the overall circuit size can be reduced.

It may so arranged that the recording means disposes the special replaydata recorded on the magnetic recording tape, taking error correctionblock for the respective replay speed as a unit, in recording areasconcentrated on oblique tracks of the magnetic recording tape.

With the above arrangement, even where there is non-linearity in thetrack, its effect can be avoided, and the special replay data can bereconstructed without being influenced by the non-linearity, and aspecial replay picture of a good quality can be obtained.

It may be so arranged that the error correction code appending meansappends, to said special replay data, error correction code set to havea minimum distance identical to that of error correction code appendedto the digital video or audio signal.

With the above arrangement, by slightly modifying the error correctiondecoder for the digital video signal or the digital audio signal, errorcorrection decoding can be achieved, and it is not necessary to add aseparate error correction decoder, so that the circuit size can bereduced.

It may be so arranged that the error correction code appending meansappends, to said intra-encoded block, error correction code havingidentical magnitude for each of the replay speeds.

With the above arrangement, special replay data can be decoded using thesame error correction decoder for various replay speeds, and the circuitsize can be reduced.

It may be so arranged that the recording means disposes the errorcorrection code in such recording areas that by scanning the magneticrecording tape once with a rotary head at a predetermined positive ornegative symmetrical replay speed (which may be either of the valuescorresponding to positive and negative tape transport speeds having thesame absolute value) during replay of the special replay data, saiderror correction code can be reconstructed.

With the above arrangement, maximum use is made of the special replaydata recording areas to form error correction blocks. Moreover, it ispossible to avoid repetition of the special replay data more thannecessary, and the sizes of the error correction blocks for therespective replay speeds can be made uniform, and the overall circuitsize can be reduced.

According to another aspect of the invention, there is provided adigital VTR for recording digital video and audio signals in respectivepredetermined areas on oblique tracks of a magnetic recording tape in apredetermined track format, and replaying from the areas, comprising:

data separating means for extracting intra-encoded data in the form ofintra-frame or intra-field data from the intra-frame or intra-fieldencoded, or inter-frame or inter-field encoded digital video signal theintra-frame or intra-field digital video signal, and the digital audiosignals, contained in an input bit stream;

recording means for recording the bit stream in areas for the digitalvideo signal, and recording the intra-encoded data extracted at the dataseparating means, in areas for the digital audio signal.

With the above arrangement, the intra-frame or intra-field, andinter-frame and inter-field encoded digital video signal and the digitalaudio signal are input in the form of a bit stream, and the bit streamis recorded in the digital video areas, while the extracted intra-frameor intra-field encoded data only is also recorded in the digital audioareas. In this way, the still replay data and slow replay data areformed.

It may be so arranged that the data separating means extracts theintra-frame or intra-field encoded data packet by packet from the bitstream in which the digital video and audio signals are mixed in theform of packets of respectively constant lengths.

With the above arrangement, intra-frame or intra-field encoded data isextracted packet by packet from the bit stream in which the digitalvideo and audio signals are mixed in the form of packets of respectivelyconstant lengths, so that the still replay data and slow replay data canbe separated packet by packet. Accordingly, the bit stream can berecorded without modification, on the magnetic tape.

It may be so arranged that the data separating means extracts theintra-frame or intra-field data macro block by macro block from the bitstream forming the digital video data of one macro block, having aplurality of luminance signal blocks and chrominance signal blockscollectively, each block consisting of 8 pixels by 8 lines.

With the above arrangement, intra-frame or intra-field data is extractedmacro block by macro block, so that the still replay data and the slowreplay data can be separated macro block by macro block. It is thereforepossible to cope with the data, formed taking a macro block as a unit,such as that of progressive refreshing.

The digital VTR may further comprise memory means for storing one frameof field of the intra encoded data extracted by said data separatingmeans, data being read from said memory means at a data rate at whichdata is recorded in the digital audio signal areas.

With the above arrangement, at least one frame or field of intra encodeddata is sequentially written, and read at a data rate at which it isrecorded in the digital audio signal areas, so that the data isextracted frame by frame or field by field. Accordingly, a still picturecan always be recorded by extracting the data frame by frame or field byfield.

The digital VTR may further comprises picture replay means for replayingvideo data for special replay, such as fast replay, still replay, andslow replay, from the intra-encoded data recorded in the digital audiosignal areas.

With the above arrangement, by replaying video data for special replay,such as fast replay, still replay and slow replay, pictures with a highdefinition can be produced.

According to another aspect of the invention, there is provided adigital VTR for recording recording digital video and audio signals inrespective designated areas of oblique tracks in a predetermined trackformat, and replaying from the areas, comprising:

data separating means for extracting intra-encoded data in the form ofintra-frame or intra-field encoded data from the intra-frame orintra-field encoded, or inter-frame or inter-field encoded digital videosignal, and the digital audio signal contained in an input bit stream;and

recording means for recording the bit stream in the digital video signalareas, and recording the intra-encoded data extracted by said dataseparating means in the digital audio signal areas, and in the digitalvideo signal areas.

With the above arrangement, the input bit stream is recorded in thedigital video areas, and the intra-frame or intra-field encoded dataextracted from the bit stream is recorded in the digital video signalareas and the digital audio signal areas, so that by using both of thedigital video signal areas and the digital audio signal areas, specialreplay data with a good picture quality can be obtained.

It may be so arranged that the recording means records a firstlow-frequency component of the intra-frame or intra-field encoded datain the digital video signal areas, and records a second low-frequencycomponent of a higher-frequency band than the first low-frequencycomponent, of the intra-frame or intra-field decoded data, in thedigital audio signal areas.

With the above arrangement, the first low-frequency component of theintra-frame or intra-field encoded data is recorded in the digital videosignal areas, and the second low-frequency component of ahigher-frequency band than the first low-frequency component is recordedin the digital audio signal areas. Accordingly, a better picture qualitycan be obtained, and the special replay image can be obtained even ifthe data in the digital audio signal areas is not reproduced.

According to another aspect of the invention, there is provided adigital VTR for recording recording digital video and audio signals inrespective designated areas of oblique tracks in a predetermined trackformat, using a rotary drum on which head of two different azimuths aremounted, comprising:

data separating means for extracting a fast replay signal from thenormal recording signal;

recording means for recording the fast replay signal in one region inone track per one scanning of the head, of the regions covered by thehead traces and in the tracks of identical azimuth;

identification signal recording means for recording an identificationsignal for identifying the track; and

replay means for replaying the identification signal.

With the above arrangement, the fast replay data can be reproduced fromone location in one track per one scanning of the head during fastreplay, so that even when the track is non-linear or the scanning traceis non-linear, the head can be scanned with reference to the region atsaid location where the fast replay data is recorded, and the data canbe accurately reproduced.

It may be so arranged that a first recording region is provided in onetrack of one azimuth in which said fast replay signal is recorded, and asecond recording region for recording the fast replay signal is alsoprovided in the track of the other azimuth, and succeeding said onetrack;

the length of the second recording region is about half the length ofthe first recording region, and the center of the second recordingregion within the track is at about the same position as the center ofthe first recording region within the track.

With the above arrangement, in the case of a drum of two-headconfiguration, the fast replay signal in the tracks of one azimuth canbe reproduced from the first recording region, while in the case offour-head configuration, the fast replay signal in the tracks of bothazimuths can be reproduced from the first and second recording regions.As a result, the total amount of fast replay data, given as the sum ofthe data from the heads of two different azimuths, is the same, and thescreen (whole picture) can be formed from the same amount of fast replaydata, regardless of the head configuration, during fast replay at thesame speed.

As a result, it is possible to obtain a device with which the fastreplay speed is not limited by the head configuration, and the fastreplay picture quality is identical regardless of the headconfiguration, and the device is therefore convenient to use.

It may be so arranged that, in the upper and lower end parts of thefirst recording region which extend out of the region corresponding tothe second recording region of the adjacent track of a differentazimuth, the signal identical to those in said second recording regionis recorded.

With the above arrangement, where the sub-regions formed by equallydividing the first recording region is called A1, A2, A3 and A4, inturn, the signals recorded in the regions A1 and A4 are extracted, andrecorded, without modification, in the second recording region, as well.In other words, the fast replay data recorded in the track of a firstazimuth is divided equally and the first and fourth quarter data arerecorded in the track of a succeeding, second azimuth. The data recordedin the track of the second azimuth can therefore be obtained by simplerearrangement means.

It may be so arranged that the recording means forms the fast replaysignal dedicated for the particular fast replay signal for each of thefast replay speeds, and records the fast replay signal at differentpositions on the magnetic recording tape.

With the above arrangement, the fast replay signals are prepared for therespective fast replay speeds, and the data is configured so that thepicture is switched at an interval which facilitates watching of thereproduced picture during fast replay at each speed.

It may be so arranged that the recording means repeatedly records thefast replay signal for (M×i)-time speed replay (i=1, 2 . . . n) atpredetermined positions in predetermined tracks of consecutive M (Mbeing a natural number) tracks, and repeatedly records the fast replaysignal for (M×i)-time speed replay, 2×i times, taking the M tracks asone unit for each speed.

With the above arrangement, the fast replay signal for the predeterminedspeed is recorded in the predetermined position in the predeterminedtrack, of the consecutive M tracks, and the fast replay signal for the(M×n)-time speed replay is repeatedly recorded 2n times, taking the Mtracks as a unit. Accordingly, during fast replay, it is sufficient ifthe control over the drum rotation and the tape transport speedperformed in such a manner that the fast replay signal recorded at onelocation in the M tracks is reproduced. For instance, when the fastreplay is effected at (M×n)-time speed, compared with the case in whichthe fast replay data is recorded at one location in M×n tracks, theamount of movement to a predetermined track in the state of transitionat the time of changing the replay speed is smaller, and thereproduction of the fast replay data at the newly selected speed can bestarted in a shorter time.

It may be so arranged that the recording means repeatedly records thefast replay signal for 4i-time speed replay (i=1, 2 . . . n) atpredetermined positions in predetermined tracks of consecutive four (Mbeing a natural number) tracks, and

said identification signal recording means records three types offrequency signals as pilot signal for tracking control on these fourtracks, being in superimposition with the digital data.

With the above arrangement, the fast replay data is disposed taking fourtracks as a unit, and the identification signals (such as the threepilot signals f0, f1 and f2 two of which (f1 and f2) may consist of twodifferent frequency signals superimposed on the digital data signal, andthe last one of which (f0) may be featured by the absence of any signalsuperimposed on the digital data signal) for tracking control arerecorded, so that, during fast replay, by the use of the identificationsignal, the desired track can be selected, and the fast replay datarecorded in the track can be reproduced.

It may be so arranged that the digital VTR further comprises errorcorrection code appending means for appending the error correction codeformed of a predetermined number of sync bits inserted at apredetermined period in the signal sequence recorded in the magneticrecording tape, a predetermined number of ID bits succeeding said syncbits, a predetermined number of first parity bits generated from the IDbits, second parity bits generated from a predetermined number ofdigital data succeeding the first parity bits, third parity bitsgenerated from a plurality of digital data extending over said syncbits, and fourth parity bits generated from the digital data andpositioned at the back of said digital data;

erroneous correction detection means for comparing the fourth paritybits with the first parity bits reproduced by said replay means, anddetecting erroneous correction on the basis of the result of comparison.

With the above arrangement, a fourth parity is appended only to thedigital data recorded in the sync blocks, and on the basis of the resultof the fourth parity check, the burst error in which the digital data iscontinuously missing in the middle of it can be detected quickly by arelatively simple comparison means.

Moreover, on the basis of such information, the erroneous correction atthe error correction decoder in a replay system at the next stage can bedetected.

It may be so arranged that the error correction code appending meansappends the fourth parity bits only to the fast replay signal.

With the above arrangement, errors can be detected promptly even in afast replay in which burst errors occur frequently due to the periodicalamplitude fluctuation in the replay signal.

According to another aspect of the invention, there is provided adigital VTR for recording digital video and audio signals, in designatedareas on oblique tracks of a magnetic recording tape, in a predefinedformat, using a rotary drum on which heads of two different azimuths aremounted, and replaying from the areas, comprising:

data separating means for extracting digital video signal (hereinafterreferred to as fast replay signal) used for fast replay, from a normalrecording signal;

recording means for recording the fast replay signals for the respectivefast replay speeds, in predefined consecutive regions in a predefinedtrack of a group of four consecutive tracks;

identification signal recording means for recording identificationsignal for identifying the tracks;

replay means for replaying the recording signal for normal replay, orfast replay signals for +2-time speed replay, or +4N-time speed replayor (-4N+2)-time speed replay (N being a positive integer); and

tracking control means for performing tracking control so that said headscans the predefined regions in the predefined track of the four tracksin accordance with the identification signal.

With the above arrangement, four tracks are taken as a unit, andidentical pattern is repeated every four tracks, and the data for eachfast replay speed is recorded in the specific consecutive sync blocks inspecific track, and during fast replay, the tracking is controlled atthe specific position on the specific track. As a result, it is possibleto increase the recording rate of the fast replay data.

It may be so arranged that the identification signal recording meanscomprises:

recording means for recording, as said identification signal, pilotsignals of two different frequencies alternately, every other tracks;and

said tracking control means includes comparison means for comparing thelevels of the identification signals of the two different frequenciescontained in the replay signal, while the head is scanning the positioncorresponding to the center of the area where the fast replay signal forthe particular fast replay speed is recorded.

With the above arrangement, during fast replay, by comparing, at aspecific timing, the levels of the identification signals of twodifferent frequencies contained in the replay signal, and effectingtracking control on the basis of the result of the comparison, the headscans the areas where the data for the respective fast replay speed isrecorded. As a result, even if the there is non-linearity in the track,or the like, it is possible to accurately track the region where thenecessary data is recorded.

It may be so arranged that the identification signal recording meanscomprises:

recording means for recording, as said identification signal, pilotsignals of two different frequencies alternately, every other tracks;and

said recording means records sync block numbers together with the fastreplay signal;

said tracking control means compares the levels of the identificationsignals of the two different frequencies contained in the replay signal,when the sync block number of the predefined sync block in the areawhere the fast replay speed signal for the particular fast replay speedis recorded, to achieve tracking control.

With the above arrangement, when the predefined sync block number isdetected during fast replay, the levels of the identification signals oftwo different frequencies are compared, to detect the tracking error,and tracking is controlled on the basis of the result of the comparison,i.e. on the basis of the detected tracking error. Accordingly, the headaccurately scans the area where the fast replay data is recorded. Thatis, even if the position at which the fast replay data is recorded isshifted in the longitudinal direction of the tape, the area where thenecessary data is recorded can be tracked accurately.

According to another aspect of the invention, there is provided adigital VTR for recording digital video and audio signals, in designatedareas on oblique tracks of a magnetic recording tape, in a predefinedformat, using a rotary drum on which heads of two different azimuths aremounted, and replaying from the areas, comprising:

data separating means for extracting digital video signal (hereinafterreferred to as fast replay signal) used for fast replay, from a normalrecording signal;

appending means for appending sync byte, ID byte, header byte to thefast replay signal, in the same sync block configuration as saidrecording signal;

recording means for recording the fast replay signal in areas on tracks,such that during fast replay, only one location on one track of anazimuth identical to the head is covered by the head scanning trace;

identification signal recording means for recording identificationsignal for identifying the tracks; and

replay means for replaying the identification signal.

With the above arrangement, the areas where normal replay data isrecorded, and the areas where fast replay data is recorded have anidentical sync block configuration, (with identical sync, ID and headerconfigurations) so that the appending means for appending sync byte, IDbyte and header byte in the recording system, and the reading means(including the ID and header reading means) can be used in common.

The digital VTR may further comprise:

input means for inputting a password from outside;

recording means for recording the password together with the digitalvideo signal;

replay means for replaying the password at the time of replay of thedigital video signal; and

replay inhibiting means for inhibiting display of the digital videosignal unless a correct password is input at the time of replay.

With the above arrangement, it is possible to protect the program or thewhole tape from unauthorized replay.

According to another aspect of the invention, there is provided adigital VTR for recording digital video and audio signals, in designatedareas on oblique tracks of a magnetic recording tape, in a predefinedformat, using a rotary drum on which heads of two different azimuths aremounted, and replaying from the areas, comprising:

data separating means for extracting digital video signal (hereinafterreferred to as fast replay signal) used for fast replay, from a normalrecording signal;

recording means for disposing a fast replay signal for an (M×i)-timespeed replay (i=1, 2 . . . n), at predefined positions on predefinedtracks of consecutive M tracks (M being a natural number), andrepeatedly recording the fast replay signal for (M×i)-time speed replay,(2×i) times;

identification signal recording means for recording identificationsignal for identifying the tracks on which the fast replay signal isrecorded; and

replay means for performing replay at an arbitrary replay speed which isan even-number of times the normal speed, and is lower than the(M×n)-time speed, using the fast replay signal recorded for (M×n)-timespeed replay.

With the above arrangement, the data recorded for (M×n)-time speedreplay can be all replayed at an even-multiple speed lower than the(M×n)-time speed, although the reproduced data may be duplicated.

According to another aspect of the invention, there is provided adigital VTR for recording digital video and audio signals, in designatedareas on oblique tracks of a magnetic recording tape, in a predefinedformat, using a rotary drum on which heads of two different azimuths aremounted, and replaying from the areas, comprising:

data separating means for extracting intra-frame encoded image data,from an input bit stream;

recording means for forming fast replay signals for a plurality of fastreplay speeds from the image data, and recording the n1-time fast speedsignal in an area therefor, at positions designated according to thecorresponding position on the screen of the signals, with the signalscorresponding to the edges of the screen being positioned at the ends ofthe recording region on the oblique track, and with the signalscorresponding to the position toward the center of the screen beingpositioned toward the center of the recording region on the obliquetrack; and

replay means for performing fast replay at an n2 time speed (n2>n1) byreplaying the n1-time fast replay signal.

With the above arrangement, the fast replay signal of the central partof the screen is collectively recorded in the center of the arearecording the n1-time fast replay signal, and replay is conducted at afast replay speed n2, higher than n1.

Accordingly, although the areas from which the signal is replayed isnarrowed because of the increase of the replay speed to n2, the centralpart of the screen can be replayed.

According to another aspect of the invention, there is provided adigital VTR for recording digital video and audio signals, in designatedareas on oblique tracks of a magnetic recording tape, in a predefinedformat, using a rotary drum on which heads of two different azimuths aremounted, and replaying from the areas, comprising:

sync block forming means for forming sync blocks by appending sync bytesto digital signal recorded in the magnetic recording tape at apredetermined interval;

data separating means for extracting a fast replay signal from thenormal recording signal;

recording means for sequentially and repeatedly recording n pieces ofdata Di (i=1, 2 . . . n, n being a natural number) each of which can berecorded in one sync block, over (n+2×w) consecutive sync blocks Sj(j=1, 2, . . . (n+2×w)) at identical positions on predefined tracks;

wherein n is a maximum number of sync blocks which can always bereproduced from the track regions overlapping with the head scanningtraces during m-time speed replay,

w is a minimum natural number which is not smaller than the maximumshift from the reference position at which the head crosses a specifictrack, during m-time speed repay.

With the above arrangement, the maximum amount of data a head canreproduce from one track at a predefined fast replay speed is recordedrepeatedly in the vicinity of the head scanning trace, taking account ofthe head position fluctuation, the maximum amount of data which isrecorded can all be reproduced during fast replay. All the data can beread during fast replay in which the effect of the head positionfluctuation is large.

It may be so arranged that the recording means repeatedly records thefast replay signal in (n+2×w) consecutive sync blocks Sj at an identicalsync block position on each track, on at least m consecutiveidentical-azimuth tracks.

With the above arrangement, the fast replay signal is repeatedlyrecorded at identical positions on consecutive tracks, so that the fastreplay signal can be replayed whichever track the head begins scanningduring fast replay.

Accordingly, control over the head scanning position is simplified, andthe fast replay at an arbitrary speed is possible as long as the headpasses the predefined track positions.

According to another aspect of the invention, there is provided adigital VTR for recording digital video and audio signals, in designatedareas on oblique tracks of a magnetic recording tape, in a predefinedformat, using a rotary drum on which heads of two different azimuths aremounted, and replaying from the areas, comprising:

sync block forming means for forming sync blocks by appending sync bytesto digital signal recorded in the magnetic recording tape at apredetermined interval;

data separating means for extracting a fast replay signal from thenormal recording signal;

recording means for sequentially and repeatedly recording p pieces ofdata Di (i=1, 2 . . . p, p being a natural number not more than n) eachof which can be recorded in one sync block, in (p+L+1) consecutive syncblocks Sj (j=1, 2 . . . (p+L+1)) at the same position in each track, inat least m tracks of consecutive identical-azimuth tracks in such amanner as to satisfy

    ek+1=mod  {ek+p-mod(p+L+1, p)}, p!

where ek and ek+1 (integers not less than 1 and not more than p) are thesuffixes i to the data D first recorded, where n is the maximum numberof sync blocks which can always be reproduced consecutively from theregion of the track on the tape overlapping with the head scanning traceduring m-time speed replay,

L is the number of sync blocks which is a minimum integer not smallerthan (D-B+C) where C is the difference between the starting positions ofthe tracks Tk and Tk+1 in the track longitudinal direction,

D is the difference between the positions, in the track longitudinaldirection, at which the head crosses with the respective tracks,

B is the length of the region from which the reproduction from one trackis possible consecutively, during m-time speed replay, and

mod a, b! expresses the remainder of a divided by b.

With the above arrangement, the arrangement of data repeatedly recordedon the tracks is such that the different data recorded on twoidentical-azimuth tracks proximate to each other and crossed by the headduring one scanning are reproduced at least once without fail, so thatthe fast replay data can be recorded with a minimum number repetitions.With the arrangement of data described above, even when the headscanning trace position fluctuates or the head trace phase is shifted,reading of the fast replay data is ensured, and images can be reproducedwith a good quality, and much fast replay data can be recorded andreproduced.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings;

FIG. 1 is a block diagram showing a recording system of a digital VTR ofEmbodiment 1;

FIG. 2A shows a transport packet of an input bit stream;

FIG. 2B shows a data packet recorded on the magnetic tape;

FIG. 3 shows a code configuration of the error correction block in adigital VTR of Embodiment 1;

FIG. 4 shows a track configuration of a digital VTR of Embodiment 1;

FIG. 5A to FIG. 5C show typical head arrangement on a rotary drum usedin the SD mode, of 1 ch×2 system, 2 ch×1 system and 2 ch×2 system,respectively;

FIG. 6 is a table showing the number of sync blocks from which data isobtainable at each replay speed;

FIG. 7A shows disposition of the special replay data recording areas inthe track in an example of recording format of a digital VTR ofEmbodiment 1;

FIG. 7B shows the data and the magnitude of the recording areas in thesame example;

FIG. 8 shows an example of manner of division of the error correctionblock in a digital VTR of Embodiment 1;

FIG. 9 shows a recording format on a track in a digital VTR ofEmbodiment 1;

FIG. 10 is a block diagram showing a replay system of a digital VTR ofEmbodiment 1;

FIG. 11 is a flow chart showing the decoding algorithm on the thirderror correction decoder;

FIG. 12 is a diagram showing the rotary head scanning trace during fastreplay in a 1 ch×2 head system;

FIG. 13A to FIG. 13C respectively show the tracking control point forthe rotary head at each of different replay speeds, for explaining thetracking control operation of a digital VTR of Embodiment 1;

FIG. 14 is a diagram showing the head scanning trace during four-timespeed replay in Embodiment 2 of the invention;

FIG. 15A and FIG. 15B respectively show the replay signals from therespective rotary heads, and the tracking control points for explainingthe tracking control operation in Embodiment 2;

FIG. 15C shows the synthesized replay data;

FIG. 16 is a block diagram showing a recording system of a digital VTRof Embodiment 3 of the invention;

FIG. 17 shows the configuration of one track in a recording format inEmbodiment 3;

FIG. 18 shows the track configuration in Embodiment 3;

FIG. 19 is a block diagram of a replay system of a digital VTR inEmbodiment 3;

FIG. 20 is a block diagram showing a recording system in Embodiment 4 ofthe invention;

FIG. 21 shows digital video data of a macro block configuration;

FIG. 22 shows coefficients of frequency components;

FIG. 23 shows dispositions in the special replay data recording areas intracks in Embodiment 4;

FIG. 24A is a block diagram showing a signal processing system in arecording system of a digital VTR in Embodiment 5 of the invention;

FIG. 24B is a block diagram showing an example of special data formingcircuit in FIG. 24A;

FIG. 25 is a block diagram showing a sync block forming circuit;

FIG. 26A to FIG. 26F show the configurations of the special replay datarecording areas in Embodiment 5;

FIG 27 shows dispositions of the special replay data recording areas intracks in Embodiment 5;

FIG. 28 is a block diagram showing a modulator in front of a recordingamplifier.

FIG. 29 shows a recording format on tracks in Embodiment 5;

FIG. 30 is a block diagram showing a special replay data forming circuitin Embodiment 6;

FIG. 31 is a block diagram showing an example of sync block formingcircuit according to Embodiment 7 of the invention;

FIG. 32 shows an example of data packet according to Embodiment 7;

FIG. 33 shows a recording format on tracks in a digital VTR according toEmbodiment 8;

FIG. 34 is a block diagram showing the configuration of a capstan servosystem;

FIG. 35 shows a specific configuration of attracting error detector inFIG. 34;

FIG. 36 shows head scanning traces during +2-time speed replay in adigital VTR in Embodiment 8;

FIG. 37 shows head scanning traces during +4-time speed replay in adigital VTR in Embodiment 8;

FIG. 38 shows head scanning traces during +16-time speed replay in adigital VTR in Embodiment 8;

FIG. 39 shows head scanning traces during +8-time speed replay in adigital VTR in Embodiment 8;

FIG. 40 shows head scanning traces during -2-time speed replay in adigital VTR in Embodiment 8;

FIG. 41 shows head scanning traces during -6-time speed replay in adigital VTR in Embodiment 8;

FIG. 42 shows head scanning traces during -14-time speed replay in adigital VTR in Embodiment 8;

FIG. 43 shows a specific configuration of a tracking error detectoraccording to Embodiment 9 of the invention;

FIG. 44 shows head scanning traces during +4-time speed replay in adigital VTR of a modification of Embodiments 8 and 9;

FIG. 45 shows head scanning traces during +4-time speed replay in adigital VTR of another modification of Embodiments 8 and 9;

FIG. 46 shows rotary head scanning traces during +4-time speed replay ofspecial replay data of a recording format according to Embodiment 10 ofthe invention, by means of a 1 ch×2 system;

FIG. 47 shows rotary head scanning traces during +4-time speed replay ofspecial replay data of a recording format according to Embodiment 10 ofthe invention, by means of a 2 ch×1 system;

FIG. 48 shows rotary head scanning traces during +4-time speed replay ofspecial replay data of a recording format according to Embodiment 10 ofthe invention, by means of a 2 ch×2 system;

FIG. 49 shows rotary head scanning traces during +8-time speed replay ofspecial replay data of a recording format according to Embodiment 10 ofthe invention, by means of a 1 ch×2 system;

FIG. 50 shows rotary head scanning traces during +8-time speed replay ofspecial replay data of a recording format according to Embodiment 10 ofthe invention, by means of a 2 ch×1 system;

FIG. 51 shows rotary head scanning traces during +8-time speed replay ofspecial replay data of a recording format according to Embodiment 10 ofthe invention, by means of a 2 ch×2 system;

FIG. 52 shows rotary head scanning traces during +16-time speed replayof special replay data of a recording format according to Embodiment 10of the invention, by means of a 1 ch×2 system;

FIG. 53 shows rotary head scanning traces during +16-time speed replayof special replay data of a recording format according to Embodiment 10of the invention, by means of a 2 ch×1 system;

FIG. 54 shows rotary head scanning traces during +16-time speed replayof special replay data of a recording format according to Embodiment 10of the invention, by means of a 2 ch×2 system;

FIG. 55 is a block diagram showing a signal processor after the errorcorrection decoding in a replay system according to Embodiment 10;

FIG. 56 is a block diagram showing a signal processor before errorcorrection decoding in a replay system according to Embodiment 11;

FIG. 57 shows an example of data packet according to Embodiment 12;

FIG. 58 shows another example of data packet according to Embodiment 12;

FIG. 59 is a lock diagram showing a signal processor after errorcorrection decoding in a replay system according to Embodiment 13;

FIG. 60A and FIG. 60B show the configuration of a password areaaccording to Embodiment 13;

FIG. 61 shows rotary head scanning traces during +6-time speed replay of8-time speed replay data of a recording format according to Embodiment14 of the invention, by means of a 1 ch×2 system;

FIG. 62 shows rotary head scanning traces during +6-time speed replay of8-time speed replay data of a recording format according to Embodiment14 of the invention, by means of a 2 ch×1 system;

FIG. 63 shows rotary head scanning traces during +6-time speed replay of8-time speed replay data of a recording format according to Embodiment14 of the invention, by means of a 2 ch×2 system;

FIG. 64 shows rotary head scanning traces during +12-time speed replayof 4-time speed replay data of a recording format according toEmbodiment 15 of the invention, by means of a 1 ch×2 system;

FIG. 65 shows rotary head scanning traces during +12-time speed replayof 4-time speed replay data of a recording format according toEmbodiment 15 of the invention, by means of a 2 ch×1 system;

FIG. 66 shows rotary head scanning traces during +12-time speed replayof 4-time speed replay data of a recording format according toEmbodiment 15 of the invention, by means of a 2 ch×2 system;

FIG. 67A shows the configuration of 4-time speed replay data recordingareas used in fast replay according to Embodiment 15;

FIG. 67B shows the position on the screen which is reproduced inEmbodiment 15;

FIG. 68 is a block diagram showing a recording system in a digital VTRin Embodiment 16;

FIG. 69 shows a rotary head scanning trace on tracks during fast replay;

FIG. 70 shows a rotary head scanning trace during replay at a 56-timespeed;

FIG. 71A shows scanning traces with which three sync blocks can bereproduced;

FIG. 71B and FIG. 71C show scanning traces which result with forward andbackward shifts in the position;

FIG. 72 shows disposition of the fast replay data according toEmbodiment 16;

FIG. 73 shows an example of disposition of fast replay data on tracksaccording to Embodiment 16;

FIG. 74 is a block diagram showing a replay system of a digital VTR inEmbodiment 16;

FIG. 75 shows the positional relationship between the scanning tracesand the fast replay data according to Embodiment 17;

FIG. 76 shows an example of disposition of fast replay data according toEmbodiment 17;

FIG. 77 shows a rotary head scanning trace during fast replay at a56-time speed according to Embodiment 18;

FIG. 78 shows sync blocks which can be reproduced when the position ofthe rotary head scanning trace is shifted;

FIG. 79 shows sync blocks which can be reproduced when the position ofthe rotary head scanning trace is shifted;

FIG. 80 shows the positional relationship between a scanning trace andthe fast replay data according to Embodiment 18;

FIG. 81A shows a scanning trace with which three sync blocks can bereproduced;

FIG. 81B shows a scanning trace with a shift in the position;

FIG. 82 shows an example of disposition of fast replay data according toEmbodiment 18;

FIG. 83 shows another example of disposition of fast replay dataaccording to Embodiment 18;

FIG. 84 shows an example of disposition of fast replay data onidentical-azimuth tracks A1 and A2, during 56-time speed replayaccording to Embodiment 18;

FIG. 85 shows another example of disposition of fast replay data onidentical-azimuth tracks A1 and A2, during 56-time speed replayaccording to Embodiment 18;

FIG. 86 shows an example of disposition of fast replay data according toEmbodiment 18;

FIG. 87 shows an example of disposition of m-time speed replay dataaccording to Embodiment 18;

FIG. 88 shows an example of disposition of fast replay data onidentical-azimuth tracks A1 and A2, during 30-time speed replayaccording to Embodiment 19;

FIG. 89 shows another example of disposition of fast replay data onidentical-azimuth tracks A1 and A2, during 30-time speed replayaccording to Embodiment 19;

FIG. 90 shows an example of disposition of fast replay data according toEmbodiment 19;

FIG. 91 shows an example of disposition of fast replay data onidentical-azimuth tracks A1 and A2, during 56-time speed replayaccording to Embodiment 19;

FIG. 92 shows an example of disposition of fast replay data onidentical-azimuth tracks A1 and A2, during 44-time speed replayaccording to Embodiment 19;

FIG. 93 shows a track pattern in a conventional common consumer digitalVTR;

FIG. 94A shows rotary head scanning traces during normal replay in aconventional digital VTR;

FIG. 94B shows a rotary head scanning trace during fast replay;

FIG. 95 is a block diagram showing an example of recording system in aconventional digital VTR;

FIG. 96A shows normal replay in an example of replay system in aconventional digital VTR;

FIG. 96B shows fast replay in the same example of replay system;

FIG. 97A a head scanning trace in a common fast replay;

FIG. 97B shows track regions from which reproduction is possible;

FIG. 98 overlapping portions of the copy areas between a plurality offast replay speeds;

FIG. 99 shows an example of rotary head scanning traces with differenttape speeds;

FIG. 100A and FIG. 100B respectively show rotary head scanning tracesduring five-time speed replay;

FIG. 101 shows a recording format on a track in a conventional digitalVTR;

FIG. 102A and FIG. 102B show an example of configurations of a trackcontaining video and audio data; and

FIG. 103 shows an example of the configuration of one sync block on amagnetic tape.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1 is a block diagram showing a recording system of a digital VTR ofan embodiment of the invention. In the drawing, reference numeral 50denotes an input terminal for receiving digital video and audio signalsin the form of a bit stream, 52 denotes a packet detector for detectingpackets of the video and audio signals from the bit stream that isreceived, 54 denotes a first memory for storing the bit stream, and 56denotes an intra detector for detecting intra-encoded data in the bitstream, 58 denotes a second memory for storing the intra-encoded dataoutput from the intra detector 56. Reference numeral 60 denotes a firsterror correction encoder for appending error correction codes to thedata output from the second memory 58. Reference numeral 62 denotes adata synthesizer for synthesizing the data output from the first memory54 and the first error correction encoder 60 to form a recording bitstream, and 64 denotes a second error correction encoder for appendingerror correction codes stipulated by the SD standard, to the recordingbit stream output from the data synthesizer 62. Reference numeral 66denotes a recording amplifier, 68 denotes a rotary drum and 70a and 70bdenote rotary heads.

FIG. 2A and FIG. 2B show an example of configuration of a packet of thedigital data. FIG. 2A shows a transport packet of the input bit stream,and FIG. 2B shows a data packet recorded on the magnetic tape. FIG. 3 isa diagram showing the configuration of the codes of an error correctionblock of the digital VTR of the embodiment of the invention. FIG. 4 is adiagram showing a track configuration of the digital VTR of anembodiment of the invention.

FIG. 5A to FIG. 5C show typical head arrangements on the rotary drumused in the SD mode. FIG. 6 is a table showing the number of sync blocksfrom which data can be obtained at each of various replay speeds. FIG.7A and FIG. 7B show an example of a recording format. FIG. 7A shows anarrangement of the special replay data recording areas, and FIG. 7Bshows the data in the recording areas and their sizes.

FIG. 8 shows an example of manner of division of the error correctionblock of the digital VTR of an embodiment of the invention. FIG. 9 showsa recording format on tracks of the digital VTR of an embodiment of theinvention.

Operation during recording of Embodiment 1 will next be described withreference to FIG. 1 to FIG. 9. The bit stream received at the inputterminal 50 contains digital video signal, the digital audio signal, anddigital data concerning the video and audio signals. The bit stream istransmitted, being divided into packets shown in FIG. 2A. Each packet isformed of a header section 92 of 4 bytes and data section 94 of 184bytes.

In Embodiment 1, the bit stream is detected, transport packet bytransport packet. Two transport packets having been detected areconverted into a recording data block of 5 sync blocks as shown in FIG.2B, and recorded. Accordingly, the transport packets of the bit streaminput via the input terminal 50 are detected by the packet detector 52,and are input in the first memory 54 and the intra detector 56.

At the first memory 54, the data of the bit stream is stored packet bypacket, and read to form the configuration of the recording data blockshown in FIG. 2B. In the example shown in FIG. 2B, the data length inone sync block is 77 bytes, and five sync blocks form two transportpackets. In the drawing, H1 denotes a first header, H2 denotes a secondheader. Recorded in the first header H1 are identification data forindication the number of the sync block in the five sync blocks, and thelike. Recorded in the second header H2 are identification data forindicating whether the data in the data section is video data or audiodata. Incidentally, in Embodiment 1, reading of data from the firstmemory 54, the second memory 58, to be described later, is conducted inaccordance with a command from the data synthesizer 62.

The bit stream output from the packet detector 52 is input to the intradetector 56, where judgement is made on whether the data in thetransport packet is intra-encoded data or not. In the MPEG2 bit stream,when the bit stream is intra-frame or intra-field encoded (intraencoded), the intra transport packets are transmitted consecutively.These are detected, and the only intra transport packets are extracted.The extracted transport packets are input to the second memory 58.

The intra-frame transport packet data input to the second memory 58 isstored packet by packet, as at the first memory 54. The data is readfrom the second memory 58 so that it is of the recording data blockconfiguration shown in FIG. 2B, like the data from the first memory 54

That is, the data length within one sync block is 77 bytes, and twotransport packets are recorded over five sync blocks. In the drawings,H1 denotes a first header having a data length of one byte, and H2denotes a second header having a data length of 2 bytes. Recorded in thefirst header H1 are identification data for discriminating each syncblock from other sync blocks in the block, identification dataindicating special replay data, and the like. Recorded in the secondheader H2 are identification data indicating the speed of the fastreplay for which the recorded special replay data is intended, and thelike. In Embodiment 1, reading from the second memory 58 is alsoconducted according to a command from the data synthesizer 62.

The special replay data read from the second memory 58, taking the fivesync blocks as a unit (data length within one sync block is 77 bytes) issupplied to the first error correction encoder 60 where error correctioncodes are appended. The operation of the first error correction encoder60 will next be described with reference to FIG. 3.

FIG. 3 shows the code configuration of the error correction codeappended to the special replay data. In embodiment 1, (85, 77, 9)Reed-Solomon code (C1 check code) identical to the error correction codeappended to the bit stream of the ATV signal, and (20, 15, 6)Reed-Solomon code (C4 check code) and having a minimum distanceidentical to that of the error correction code for the audio signal areused in the recording direction and in the vertical direction, both asfirst error correction code for the special replay data.

The special replay data is read from the second memory 58, five syncblocks as a unit, and 15 sync blocks are collected at the first errorcorrection encoder 60, and one error correction block is formed of the15 sync blocks. C4 check code is appended in the vertical direction, andthe C1 check code in the recording direction is appended at the seconderror correction encoder 64, in the same way as the ATV signal outputfrom the first memory 54, and the error correction block of the productconfiguration is formed.

Because the minimum distance of the C4 check code is identical to the C3check code of the audio signal, the encoder may be used in common, bysimply switching the code length. The code length is 14 in the case ofthe audio signal, and is 20 in the case of the special replay data.

With the track configuration of the SD (of the current televisionsystem) shown in FIG. 4, 149 sync blocks are provided per track for anarea 96 for recording video data, as described in connection with theprior art example (or FIG. 102A and FIG. 102B). Out of the 149 syncblocks, three blocks are used for recording VAUX data, and eleven blocksare used for recording error correction code (C2 check code). One syncblock is formed of 90 bytes as in the prior art example shown in FIG.103. Out of the 90 bytes, five bytes at the head are used for recordinga sync pattern and an ID signal, and eight bytes at the tail are usedfor recording error correction code (C1 check code), as shown in FIG. 4.The data which can be recorded in one sync block is therefore 77 bytesas shown in FIG. 103 and FIG. 4.

The data synthesizing operation at the data synthesizer 62 will next bedescribed with reference to FIG. 5A to FIG. 9.

FIG. 5A to FIG. 5C show different arrangements of the heads on therotary drum, and respectively show 1 ch×2 system in which two heads aredisposed in opposition, 2 ch×2 system in which two heads are juxtaposed,and 2 ch×2 system in which two sets of heads are disposed in opposition.The angle over which the magnetic tape is wrapped around the drum is180°. In FIG. 6, the number of the sync blocks from which data can beobtained from one track at each of the replay speeds is shown. In thedrawing, 9000 rpm system means the system having the heads as shown inFIG. 5A and FIG. 5B, and 4500 rpm system means the system having theheads as shown in FIG. 5C. The track pitch in the SD standard is 10 μm,and the values in the drawing show the number of sync blocks per trackwhich can be replayed at each of the replay speeds, where special replayis conducted using a rotary head having a width of 10 μm. It is assumedin the calculation that the number of sync blocks per track(corresponding to 180°) is 186 (see FIG. 4), and as in the prior artexample the data can be obtained from the part where the output level ofthe replay signal is greater than -6 dB.

FIG. 7A shows the arrangement of the special replay data recording areasin the tracks of a digital VTR of Embodiment 1 of the invention, takingaccount of the number of sync blocks from which data can be obtained asshown in FIG. 6. In this recording format, the special replay datarecording areas are repeated at an interval of four tracks, and thespecial replay data recording areas for each of the fast replay speedsare provided on the four tracks 98, 100, 102 and 104 forming oneinterval. In the drawing, aa1 and aa2 indicate special replay data for2-time speed, 4-time speed and -2-time speed, and bb1 and bb2 indicatespecial replay data for 8-time speed and -6-time speed, and cc1 and cc2indicate special replay data for 16-time speed, and -14-time speed.Provided in the first track 98 is a recording area for the specialreplay data bb1. Provided in the second track 100 is a recording areafor the special replay data bb2. Provided in the third track 102 arerecording areas for the special replay data aa1 and cc1. Provided in thefourth track 104 are recording areas for the special replay data aa2 andcc2.

FIG. 7B shows data (the number of sync blocks) recorded in each of thespecial replay data recording areas. FIG. 8 shows an example of mannerof division of an error correction block at 16-time speed(-14-timespeed). In FIG. 7B, identical signals are recorded in the recordingareas designated with identical reference marks. For instance, data #1in special replay data aa1 is recorded also as special replay data aa2.The special replay data aa1 and aa2 are repeatedly recorded over twotracks as shown in FIG. 9. The special replay data bb1 and bb2 arerepeatedly recorded over four tracks as shown in FIG. 9.

Referring to FIG. 8, twenty sync blocks of the special replay data cc1and cc2 for the 16-time speed and -14-time speed form one errorcorrection block, with the above-mentioned error correction codes (C1and C4 codes) being appended, which is divided into four sections, eachconsisting of five sync blocks. The data #8a and #9a of two upper blocksare repeatedly recorded over eight tracks, and the data #8b and #9b(ECC) of the two lower blocks are repeatedly recorded over eight tracks.

FIG. 9 shows a recording format of the special replay data for 27tracks. Recording areas for the special replay data aa1, aa2, aa3, . . .bb1, bb2, bb3, . . . cc1, cc2, cc3, . . . are repeated at an interval offour tracks on the magnetic tape. The areas designated with identicalreference marks are used for recording identical special replay data.

The operation during the special replay is next described with referenceto FIG. 9.

With reference to FIG. 6, in a system of 9000 rpm, data of 62 sync blockcan be reproduced at four-time speed, while in a system of 4500 rpm,data of only 31 sync blocks can be reproduced. With the recording formatshown in FIG. 9, in a system of 9000 rpm, all the special replay dataaa1 recorded in one track can be reproduced, at four-time speed replay.This is because, as shown in FIG. 7B, data #1, #2, #3 and #4 are 40 SBsin all, all the signals can be reproduced, In a system of 4500 rpm,however, about 9 sync blocks can be reproduced.

Accordingly, of the special replay data aa1 shown in FIG. 7B, data ofseveral sync blocks at the head of data #1, and data of several syncblocks at the tail of data #4 cannot be reproduced. In the digital VTRof Embodiment 1 of the present invention, auxiliary data for use in asystem of 4500 rpm is recorded as the special replay data aa2. (Themanner of configuring one error correction block in a system of 4500 rpmwill later be described in connection with Embodiment 2.)

Referring again to FIG. 1, the data output from the first memory 54 andthe first error correction encoder 60 are input to the data synthesizer62, at which the data from the first memory 54 and the first errorcorrection encoder 60 are synthesized, to form a predetermined trackformat. The operation of the data synthesizer 62 will next be describedbriefly.

Five sync blocks of the bit stream of the ATV signal stored in the firstmemory 54 form two transport packets, as shown in FIG. 2B, and the bitstream is read from the first memory 54, one sync block as a unit, at apredetermined timing, and are disposed in areas other than the specialreplay data recording areas in the ATV areas (hereinafter referred to asmain areas) on the recording tracks in FIG. 4. The data synthesizer 62generates a control signal for controlling the timing of reading thedata from the first memory 54, and the data read out are synthesized onthe basis thereof.

The data of the 20 sync blocks having the error correction code appendedat the first error correction encoder 60 is output to the datasynthesizer 62 at a predetermined timing. Specifically, prior to thetime (delay time) necessary for the formation of the error correctioncode from the second memory 58, a control signal for reading data fromthe second memory 58 is output from the data synthesizer 62. That is,the data synthesizer 62 synthesizes the data from the first memory 54and the second memory 58, to form a recording format shown in FIG. 9.The ATV signal synthesized into a predetermined format at the datasynthesizer 62, and recorded in the vide areas for one track, and thespecial replay data having the C4 check code appended is input to thesecond error correction encoder 64. At the data synthesizer 62, thetrack format for each track is formed, so that four tracks form a onecycle. In Embodiment 1, the recording of the special replay datarepeated according to each of the replay speeds is prepared in thesecond memory 58. That is, memory regions for storing data for each ofthe replay speeds are prepared in the memory 58, and the data isrefreshed at a predetermined period.

In the second error correction encoder 64, error correction code (C2check code) is appended, in the vertical direction, to the data recordedin the video areas synthesized at the data synthesizer 62, and the errorcorrection code (C1 check code) is appended, in the recording direction,thereafter. Thus, the C1 check code is appended to the special replaydata shown in FIG. 3, at this timing. The recording data having theerror correction code appended are subject to digital modulation, andamplified at the recording amplifier 66, and recorded on the magnetictape by means of the rotary heads 70a and 70b.

FIG. 10 shows a block diagram of a replay system of a digital VTR of anembodiment of the invention. In the drawing, the rotary drum 68, therotary heads 70a and 70b are identical to those in FIG. 1. Referencenumeral 72 denotes a head amplifier, 74 denotes a signal detector fordetecting digital data from the replay signal, and 76 denotes a digitaldemodulator for applying digital demodulation to the replay digital dataoutput from the signal detector 74. Reference numeral 78 denotes a firsterror correction decoder for correcting or detecting errors contained inthe replay signal, using the C1 check code (the error correction code inthe recording direction), 80 denotes a second error correction decoderfor correcting or detecting errors which have not been corrected by theC1 check code (errors detected, or not detected), using the C2 checkcode (the error correction code appended to the video signal in thevertical direction), 82 denotes a third memory, 84 denotes a third errorcorrection decoder for correcting or detecting errors, using the errorcorrection code (hereinafter referred to as C4 check code) in thevertical direction for the special replay data shown in FIG. 3, duringreplay of the ATV signal, 86 denotes a fourth memory, 88 denotes aswitch, and 90 denotes a data output terminal.

FIG. 11 shows a decoding algorithm in the third error correctingdecoder. FIG. 12 shows scanning traces of the rotary head 70a in adigital VTR at fast replays in a 1 ch×2 head system.

The numerals "2", "4", "8", and "16" at the starting points of thearrows in the drawing indicate that the respective arrows are scanningtraces for double speed replay, four-time speed replay, eight-time speedreplay, and 16-time speed replay are conducted with the digital VTR.

FIG. 13A to FIG. 13C are for explaining the tracking control operationin a digital VTR of an embodiment of the invention. FIG. 13A to FIG. 13Crespectively show tracking control points of the rotary head at therespective replay speeds. They show the tracking control positions, andthe output patterns of the replay signal output from the rotary head 70awhich result when double speed replay, four-time speed replay,eight-time speed replay and 16-time speed replay are conducted in adigital VTR having a rotary head configuration shown in FIG. 5A or FIG.5B.

The operation of the replay system will next be described with referenceto FIG. 10 to FIG. 13.

During normal replay, data replayed via the rotary heads 70a and 70bfrom the magnetic tape is amplified at the head amplifier 72, and asignal is detected at the signal detector 74, and converted into replaydigital data at the digital demodulator 76. The digital-demodulatedsignal is subjected to error correction and detection at the first errorcorrection decoder 78, using the C1 check code appended in the recordingdirection (this decoding will herein after referred to as C1 decoding).The error-corrected data is input to the second error correction decoder80 and the third error correction decoder 84.

At the second error correction decoder 80, error correction or decodingis conducted using the C2 check code (error correction code appended inthe vertical direction) for the data which have not been error-correctedby the C1 check code (the data for which an error has been detected, andthe data which contains an undetected error). This error correctiondecoding is hereinafter referred to as C2 decoding. The data havingreceived the C2 decoding is input to the third memory 82, where the bitstream of the ATV signal is separated from the input data, and only thebit stream is stored in the memory. The special replay data is discardedat this stage, as in the prior art example.

At the third error correction decoder 84, data replayed from the specialreplay data recording areas is separated from the data input to thethird error correction decoder 84, to form one error correction blockshown in FIG. 3. The separation of the data from the special replay datarecording areas is accomplished by detecting the positions of thespecial replay data recording areas on the track by referring to thesync block numbers recorded in the ID signals in the sync blocks, anddetecting the identification data in the header H2 in the sync blocks,and judging whether the data is the special replay data or the bitstream of the ATV signal.

When the above-mentioned one error correction block is formed, the thirderror correction decoder 84 conducts error correction or detection onthe data which has not been error-corrected (the data for which an errorhas been detected, and the data which contains an undetected error) withthe C1 check code, using the C4 check code (error correction codeappended in the vertical direction of the special replay data). Thisdecoding is hereinafter referred to as C4 decoding. The data havingreceived the C4 decoding is input to the fourth memory 86.

In Embodiment 1, the minimum distance of the C4 check code for thespecial replay data, and the minimum distance for the C3 check code forthe audio data are made to be identical. The reason for this is asfollows. The audio signal in the ATV signal is transmitted together withthe digital video signal, it is recorded in the video signal areas,rather than in separate audio signal areas. Accordingly, during replayfrom a magnetic tape of the digital VTR recording the ATV signal, theerror correction decoder for the audio signal is not used. In Embodiment4, by making the minimum distance of the C4 check code and the minimumdistance of the C3 check code identical, as described above, the thirderror correction decoder 84 is used also as the error correction decoderfor the audio signal. In this way, the size of the circuit is reduced.There is however some addition of circuits. This will be laterdescribed.

The fourth memory 86 stores the special replay data having beensubjected to the error correction. During normal replay, the dataselector 88 selects the output of the third memory 82, and the bitstream of the ATV signal restored at the third memory 82 into packetinformation of 188 bytes is output via the output terminal 90.

The operation in the still mode will next be described.

The still replay may be started by transition from a normal replay, orby selection in the state of halting. First, description is made for thecase where the still replay is started by transition from normal replay.

When the still mode is selected during normal replay, the replay data isstopped, and input of data to the third memory 82 and the fourth memory86 is interrupted. The selector 88 selects the output of the fourthmemory 86 to output the still picture via the output terminal 90. Datashown in FIG. 2B, other than H1 and H2, i.e., the data of the transportpacket is stored in the third and fourth memories 82 and 86. Theintra-encoded data having received the error-correction at the thirderror correction decoder 84 is stored in the fourth memory 86, so thatit is only necessary to sequentially read the data stored, transportpacket by transport packet. The configuration may be such that, duringstill replay, the data of the transport packets replayed from thespecial replay data recording areas for the double speed, four-timespeed and -2-time speed having the most recording data amount is output.During normal replay, as the data used for still replay, the specialreplay data for 2-time, 4-time or -2-time speed replay may be decoded,and stored for use as the data for still replay.

Next, the situation where the still mode is selected from the state ofhalting is described. In the state of halting, no data is present in thethird and fourth memories 82 and 86. If, in this state, the still modeis selected, it is necessary to conduct normal replay to store the datafor one screen in the fourth memory 86, and stop the tape. In the caseof still replay, the still mode signal is output to the decoder of theATV, and the still picture may be formed at the memory of the ATV.Alternatively, transport packets indicating no motion compensationprediction error (i.e., the transport packets indicating a stillpicture) may be formed at the digital VTR and is kept output.

The operation during fast replay will next be described.

The description will be made with regard to the rotary headconfiguration shown in FIG. 5A. FIG. 12 shows scanning traces of therotary head 70a which result when replay is made at double speed,four-time speed, eight-time speed and 16-time speed. The scanning tracesof the rotary head also result when the rotary head configuration is asshown in FIG. 5B. However, with regard to the head 70b, the traces willbe entirely different because of the different head disposition.

First, the tracking control system during fast replay in Embodiment 1 isdescribed with reference to FIG. 12 and FIG. 13A to FIG. 13C. Duringfast replay, the data is intermittently replayed, as described above.The number of sync blocks replayed from one track at the respectivereplay speeds is as shown in FIG. 6. The special replay data can beobtained effectively, by controlling the tracking of the rotary head 70aso as to maximize the replay output around the areas where the specialreplay data is recorded at the respective replay speeds. FIG. 13A toFIG. 13C show the tracking control points for the rotary head 70a at therespective replay speeds. With the recording format shown in Embodiment1, in a system of 9000 rpm, the data of one error correction block shownin FIG. 3 can be formed without using the data replayed via the rotaryhead 70b. Accordingly, FIG. 12 omits showing the scanning traces of therotary head 70b.

The operation of the replay system during fast replay will next bedescribed with reference to FIG. 10 to FIG. 13C. When a fast replay modesignal is input, the selector selects the output of the fourth memory86. The replay data intermittently replayed via the rotary heads 70a and70b is amplified at the head amplifier 72, and converted to the replaydigital data at the signal detector 74, and digital-decoded at thedigital decoder 76. The data having its sync data correctly detected atthe signal detector 74 is subjected to error correction using the C1check code at the first error correction decoder 78. The C1-decoded datais input to the third error correction decoder 78. The output of thefirst error correction decoder 78 is also input to the second errorcorrection decoder 80, but as the data is intermittently replayed, C2decoding cannot be conducted, and transport packets cannot be generated.

The operation of the third error correction decoder 84 will next bedescribed with reference to FIG. 11 and FIG. 12.

From the data input to the third error correction decoder 84, the datafrom the special replay data recording areas is detected, and one errorcorrection block shown in FIG. 3 is formed. The separation of the datafrom the special replay data recording areas is accomplished bydetecting the positions of the special replay data recording areas onthe track by referring to the sync block numbers recorded in the IDsignals in the sync blocks, and Judging whether the data is the bitstream of the ATV signal or the special replay data by referring to theheader in the sync block.

When one error correction block is thus formed, the third errorcorrection decoder 84 conducts decoding using the C4 code according tothe algorithm shown in FIG. 11. When data of one error correction blockis formed, the third error correction decoder 84 judges whether thereplay mode is the one for selecting the ATV signal or not according tothe control signal output from a system controller, not shown (step106). If the replay mode is not the one for selecting the ATV signal,the code length k for conducting the C3 decoding is set to be "14" (step108). If the replay mode is the one for selecting the ATV signal, thecode length k is set to be "20" (step 110). When the code length is set,the third error correction decoder 84 sets the erasure positionsdetected at the time of C1 decoding, in the third error correctiondecoder 84 (step 112). Then, the syndrome for the case where the codelength k equals to "20" is formed on the basis of the erasure positions(step 114). For using the circuits in common with the C3 decoding of theaudio signal, it is necessary to add a selector for changing the initialvalue of the counter counting the code length.

When the syndrome is formed, on the basis of the result of the syndromeformation, calculation of the error position polynomial and the errorvalue polynomial is conducted (step 116). This part can be used incommon with the C3 decoding because the minimum distance is equal. Inthe Chien search, the error positions and error values are determined onthe basis of the error positions and the coefficient data of the errorpolynomial (step 118). To use the circuits in common with the C3decoding of the audio signal, it is necessary to add a selector foraltering the initial value of the Chien search, and a selector foraltering the initial value of the counter counting the code length. Theerror correction is effected on the basis of the error positions and theerror values (step 120). The above steps are repeated until all the dataof one correction block is completed (step 122). The C4-decoded specialreplay data is input to the fourth memory 86. From the fourth memory 86,the ATV bit stream having been restored into packet information of 188bytes is output via the selector 88 and the output terminal 90.

The manner of configuring the error correction block shown in FIG. 3will next be described. In the digital VTR of Embodiment 1, the mannerof configuring one error correction block differs between the low-speedfast replay (double speed, four-time speed, -2-time speed, eight-timespeed and -6-time speed), and high-speed fast replay (16-time speed and-14-time speed). This is because the number of the sync blocks replayedby the rotary head 70a is "12" which is smaller in the case of the16-time replay. Accordingly, all the data forming one error correctionblock is not replayed during one scanning by the rotary head 70a, andthe data is disposed on the recording tracks so that one errorcorrection block is formed by two scannings of the rotary head 70a. Thisis because changing the minimum distance of the error correction codecauses increase of the size of the circuit of the error correctiondecoder.

Accordingly, if, only for the 16-time speed (-14-time speed), theminimum distance were made to be identical only for the 16-time speed(-14-time speed) replay data and the size of the error correction blockwere altered, then five or six sync blocks of special replay data wouldbe obtained for five sync block of error correction code, so that therate of data collection would be low. It is for this reason that, inEmbodiment 1, data is disposed on the recording tracks such that data ofan error correction block identical to that in other fast replay speedscan be formed over two scanning periods by the rotary head 70a.

The manner of configuring one error correction block in the case ofdouble speed, four-time speed and -2-time speed will next be described.As illustrated in FIG. 12, in the case of double speed replay, the partaa1 is replayed during one scanning period of the rotary head 70a. Asillustrated in FIG. 7B, data of two error correction blocks is disposedin the part aa1, so that the third error correction decoder 84 appliesC4 decoding to each of the error correction blocks. In the case ofdouble speed replay, identical error correction block is replayed twice,the decoding may be conducted only one of the error correction blocks.The control will be the same for the reverse double speed repay (-2-timespeed). In the case of the four-time speed replay, the data of the partaa1 is replayed during one scanning period of the rotary head, so thatthe operation is similar to that for the double speed.

During eight-time speed replay, the data of part bb1 is replayed duringone scanning period of the rotary head. As shown in FIG. 7B, data of oneerror correction block is disposed in the part bb1, so that the thirderror correction decoder 84 conducts C4 decoding when the data of partbb1 is replayed. In the case of -6-time speed replay, the operation issimilar, but an identical error correction block is replayed one out offive rotations, so that this block need not be decoded. In the case of16-time speed replay, as shown in FIG. 6, the data replayed from onetrack consists of 12 sync blocks, one error correction block cannot beconfigured from data replayed from one track only. Accordingly, inEmbodiment 1, the 16-time speed replay data is divided into two tracks(see FIG. 7).

In this way, the third error correction decoder 84 configures one errorcorrection block from the data replayed over two scanning periods of therotary heads 70a, and conducts the C4 decoding. During the firstscanning period, 10 sync blocks including the data #8a and #9a arereplayed, and, in the next scanning period, 10 sync blocks including thedata #8b and #9b are replayed, and one error correction block is therebyconfigured.

The operation in the slow replay will next be described.

During slow replay, the speed of magnetic tape transport is lower thanin normal replay, and each oblique track is scanned and replayed severaltimes as the tape is transported. Accordingly, of the replay digitalsignal, the data for which the sync signals have been correctly detectedat the signal detector 74, and the sync blocks have been correctlydecoded at the digital decoder 76 is extracted, and is subjected toerror correction using the C1 check code, and the replay data for doublespeed, four-time speed and -4-time speed stored in the special replaydata recording areas is extracted, and output to the third errorcorrection decoder 84. The separation of the data can be accomplished,as in normal replay, by detecting the positions within the track, byreferring to the ID signals contained in the sync blocks, andidentifying the track by referring to the header information recorded inthe data areas.

The third error correction decoder 84 configures one error correctionblock using the above mentioned data, and conducts C4 decoding as innormal replay. The C4-decoded data is stored in the fourth memory 86.The fourth memory 86 synthesizes a still picture, and data storedtransport packet by transport packet is sequentially read. The selector88 selects the output of the fourth memory 86.

As described in connection with the prior-art example, during specialreplay (slow replay, fast replay, etc.), the rotary head crosses therecording tracks obliquely, so that the replay signal obtained from thetracks is intermittent. As a result, the error correction block (videodata) shown in FIG. 102A cannot be obtained as in the prior art example.However, in Embodiment 1, one error correction block for special replayshown in FIG. 3 is formed and recorded, so that it is possible toconduct error correction using the C4 check code for the data for whicherror correction using the C1 check code was not conducted. As aconsequence, in the case where the symbol error rate is 0.01, the errordetection rate will be 1.54×10⁻¹³, and the error detection rate isimproved by 10¹⁰, so that it is a level which is practicallysatisfactory. The undetected error rate is also 2.38'10⁻¹⁶, which ispractically satisfactory.

In addition, as described in connection with the prior art example, itoften happens that the symbol error rate is 0.01 or more during specialreplay. However, with regard to the result of calculation, the errorrate is of the practically satisfactory level when the above codeconfiguration is used, so that satisfactory special pictures can beobtained.

Embodiment 2

In Embodiment 2, description is made of the operation of a system of4500 rpm shown in FIG. 5C. It is assumed that the recording format isthe same as in Embodiment 1. The operation during normal replay, stillreplay, and slow replay is identical to that in Embodiment 1, so itsdescription is omitted, and the description is made only in connectionwith the fast replay.

FIG. 14 shows the scanning traces of the rotary head at the time offour-time speed replay in Embodiment 2. In the drawing, the scanningtraces of the rotary heads 70a and 70b are shown by arrows. The methodof tracking control during fast replay in Embodiment 2 is similar tothat in Embodiment 1, and the tracking of the rotary head 70a iscontrolled so that the replay output is maximum around the areas wherethe special replay data is recorded.

The operation of the replay system of Embodiment 2 will next bedescribed referring also to FIG. 10. When the fast replay mode signal isinput, the selector 88 selects the output of the memory 86. The replaydata obtained intermittently via the rotary heads 70a and 70b isamplified at the head amplifier 72, and converted into replay digitaldata at the signal detector 74, and digital decoded at the digitaldecoder 76. The data for which the sync data is correctly detected atthe signal detector 74 is subjected to error correction using the C1check code at the first error correction decoder 78. The C1-decoded datais input to the third error correction decoder 84. In the system of 4500rpm shown in FIG. 5C, the same number of replay signal systems (from thehead amplifier 72 to the first error correction decoder 78) as thenumber of the channels (i.e., two) are provided, although not shown assuch, as it does not relate to the essential feature of Embodiment 2.

With regard to the data input to the third error correction decoder 84,the data from the special replay data recording areas is detected, andone error correction block shown in FIG. 3 is formed. In a system of4500 rpm, the number of sync blocks replayed from one track duringfour-time speed replay is 31 as shown in FIG. 6. It is therefore notpossible to configure one error correction block from the data replayedby the rotary head 70a. That is, data necessary to form an intra-pictureof one frame is not replayed.

FIG. 15A to FIG. 15C are for explaining the tracking control operationin Embodiment 2. FIG. 15A and FIG. 15B show the replay signal replayedby the respective rotary heads, and the tracking control points. FIG.15C shows the synthesized replay data. In the drawing, in the partsdesignated with identical reference marks (the parts designated by "#1"and "#4"), identical data is recorded.

In the system of 4500 rpm, auxiliary data replayed by the head 70b isused to form data of one error correction block. That is, duringfour-time speed replay, a first error correction block is formed bycombining the data #1 replayed by the rotary head 70b and the data #2replayed by the rotary head 70a, and a second error correcting block isformed by combining the data #3 replayed by the rotary head 70a and thedata #4 replayed by the rotary head 70b. FIG. 15C shows two errorcorrection blocks configured in the above described manner. Theseparation of the data from the special replay data recording areas isaccomplished by detecting the positions of the special replay datarecording areas by referring to the sync block numbers recorded in theID signals in the sync blocks, and judging whether the data is from thebit stream of the ATV signal or the special replay data by referring tothe headers in the sync blocks.

When the data of one error correction block is configured, the thirderror correction decoder 84 conducts the decoding using the C4 codeaccording to the algorithm shown in FIG. 11. The operation of the C4decoding is similar to that in Embodiment 1, so that its detaileddescription is omitted. The C4-decoded special replay data is input tothe fourth memory 86. The ATV bit stream having been restored into thepacket information of 188 bytes in the fourth memory 86 is output viathe selector 88 and the output terminal 90.

In Embodiment 2, description is made of the case of four-time speedreplay. However, fast replay can be similarly effected at the doublespeed, -2-time speed, 8-time speed, -6-time speed, 16-time speed, or-14-time, as in Embodiment 1. Moreover, by using the special replayauxiliary data reproduced by the rotary head 70b, one error correctionblock can be formed in the system of 4500 rpm, like Embodiment 1. Thatis, data necessary for forming an intra picture of one frame can bereproduced. With regard to 16-time speed and -14-time speed replay, oneerror correction block is formed by two scannings of the rotary heads70a and 70b.

For special replay (slow replay, fast replay), the rotary head crossesthe recording tracks obliquely, so that the replay signal is obtainedintermittently from the respective tracks. Accordingly, error correctionblocks (video data) shown in FIG. 102A is not formed in this embodiment,like the prior art example. However, one error correction block shown inFIG. 3 can be formed by the use of the special replay auxiliary datareproduced by the rotary head 70b in the system of 4500 rpm described inconnection with Embodiment 2. It is therefore possible to apply errorcorrection using C4 check code on the data whose errors were notcorrected by the error correction using the C1 check code. The errordetection probability for the symbol error rate of 0.01 is about1.54×10⁻¹³, and the error detection probability is improved by 10¹⁰times, and practically satisfactory results are obtained. Undetectederror rate will be about 2.38×10⁻¹⁶, which is practically satisfactory.

As described in connection with the prior art example, the symbol errorrate is often more than 0.01 during special replay, but as far as theresult of calculation concerning the error rate, practicallysatisfactory levels are attained with the above code configuration, andspecial replay pictures with good qualities are obtained. That is, therecording formats described in connection with Embodiment 1 is alsosuitable for all the rotary head arrangements shown in FIG. 5A to FIG.5C.

In Embodiment 1 and Embodiment 2, sync block special replay datarecording areas are disposed on the recording tracks such that an errorcorrection block is formed by one scanning of the rotary head 70a at thelow-speed special replay speed (still replay, slow replay, and double,four-time and eight-time speed replay). Accordingly, the storagecapacity of the memory in the third error correction decoder 84 forforming one error correction block can be reduced. Moreover, the timingsfor control over writing of replay data into the memory and reading fromthe memory, and starting the error correction are synchronized with therotation of the rotary head 70a, and the control over the memory and theerror correction decoder is simplified, and the size of the circuit canbe reduced.

In Embodiment 1 and Embodiment 2, where special replay is conducted atpredetermined replay speeds, the special replay data recording areas forthe respective replay speeds are disposed collectively at predeterminedpositions on the tracks, as shown in FIG. 7A and FIG. 7B or FIG. 9. Thisis for the following reason. During fast replay, the tracking control iseffected at the central parts of the special replay data recording area,as described above, so that if they were disposed over a plurality oftracks, it could happen that the predetermined areas cannot be replayedbecause of the non-linearity inherent to a VTR.

If the special replay data for the respective replay speed iscollectively recorded, the special replay data can be replayed withoutbeing influenced by the non-linearity of the tracks so much, and aspecial replay picture with a good quality can be obtained.

In Embodiment 1 and Embodiment 2, the minimum distance of the errorcorrection code appended at the error correction appending means isidentical to the minimum distance of the error correction code appendedto the digital audio signal. With this feature, by slightly modifyingthe error correction circuit for the digital video signal or the digitalaudio signal, error correction decoding can be achieved without adding aseparate error correction circuit, and the size of the circuit can bereduced.

In particular, in Embodiment 1, the minimum distance of the errorcorrection code appended at the error correction appending means isidentical to the minimum distance of the CS code for the audio signal.It is sufficient, in connection with the decoding, to add a circuit forsetting the value of the counter counting the code length of thesyndrome forming circuit, and a circuit for setting the value of thecounter counting the number of times of Chien search. In Embodiment 1,the minimum distance of the error correction code appended at the errorcorrection appending means is identical to the minimum distance of theC3 code for the audio signal. The invention is not limited to this, andit may be identical to the minimum distance of the C1 code (the C1decoder decodes only the special replay data during special replay, sothat it has time to spare), or of the C2 code (C2 decoding is notconducted during special decoding), and yet similar effects areobtained.

In Embodiment 1 and Embodiment 2, the error correction blocks are soformed that the size of one error correction block is identical for therespective replay speeds, so that the decoding of the special replaydata can be decoded at an identical error correction circuit. As aresult, the size of the circuit can be reduced.

Where the block size of the error correction block is changed for therespective replay speeds, it is so arranged that the minimum distance ofthe error correction code within one error correction block is made tobe identical for the respective replay speed. With such an arrangement,the error correction decoder can be used in common, by simply adding aselector circuit for setting an initial value of the code length settingcounter at the time of syndrome formation, and the initial values of theregisters and the initial value of the code length setting counter atthe time of Chien search. The effects similar to those described (suchas the reduction in the circuit size) can also be obtained.

In Embodiment 1 and Embodiment 2, the predetermined replay speeds arethose corresponding to positive and negative tape transport speedshaving the same absolute value. In this connection, it should be notedthat +n-time replay speed and -(n-2)-time replay speed (n being anarbitrary number larger than 1) correspond to positive and negative tapetransport speeds having the same absolute value. Because thepredetermined replay speeds are set as described above, it is possibleto use the special replay data recording area for the positive andnegative symmetrical speeds for which the data amount (the number ofsync blocks) reproduced from one track at the replay speedscorresponding to positive and negative tape transport speeds having thesame absolute value, and the maximum use can be made of the specialreplay data recording areas to form one error correction block. Inparticular, in the case of a high-speed fast replay, the number of syncblocks replayed from one track is very small, as shown in FIG. 6.Accordingly, the special replay speeds are set to be valuescorresponding to positive and negative tape transport speeds having thesame absolute value, and the special replay data recording areas are sodisposed on the recording tracks that one block is formed by twoscannings of the rotary head, so that it is not necessary to repeatspecial replay data more than necessary. Moreover, the size of one errorcorrection block for the respective replay speeds can be made to beidentical, and the circuit size can be reduced.

In connection with Embodiment 1 and Embodiment 2, description is madewith respect to the cases where the replay speed is 2-time, 4-time,8-time, 16-time, -2-time, -6-time, and -14-time speed. In the digitalVTR having a recording format shown in FIG. 7A and FIG. 7B, satisfactoryspecial replay can be achieved at any arbitrary speed of from -14-timeto 14-time speed, and the effects similar to those described above(including the reduction of the circuit size) can also be achieved.

In Embodiment 1 and Embodiment 2, description is made of the digital VTRhaving the recording format shown in FIG. 9. However, the invention isnot limited to this. Similar effects are obtained with any otherrecording format as long as it can be used for recording a specialreplay signal with new error correction code appended to it. The errorcorrection code configuration is not limited to that shown in FIG. 3.

Embodiment 3

FIG. 6 is a block diagram showing an example of a recording system of adigital VTR of Embodiment 3 of the invention. In FIG. 6, referencenumeral 50 denotes an input terminal for receiving digital video andaudio signals in the form of a bit stream, 52 denotes a packet detectorfor detecting packets of video and audio signals from the bit stream, 54denotes a first memory for storing the bit stream, 130 denotes a thirderror correction encoder for forming video areas and conducting errorcorrection encoding, 56 denotes an intra detector for detecting intraencoded data from the bit stream, 58 denotes a second memory for storingthe intra encoded data, 132 denotes a fourth error correcting encoderfor forming audio areas and conducting error correction encoding, 134denotes a digital modulator for conversion into data suitable forrecording on the magnetic tape, 66 denotes a recording amplifier, 68denotes a rotary drum, and 70a and 70b denote magnetic heads.

FIG. 17 shows the recording format on the tracks in Embodiment 3. FIG.17(A) shows the configuration of the entire track, FIG. 17(B) is anenlarged view of the audio area, FIG. 17(C) shows the configuration of async block (SB #0) in the data area, and FIG. 17(D) shows theconfiguration of another sync block (SB #13).

FIG. 18 shows the track configuration in Embodiment 3, and shows thedata format of the audio area 136 and the video area 138.

The operation during recording will next be described with reference toFIG. 16 to FIG. 18, as well as FIG. 2A and FIG. 2B.

Referring in particular to FIG. 16, the bit stream received at the inputterminal 50 contains digital video and audio signals, and digital dataconcerning the video and audio signals. It is transmitted, beingpartitioned into transport packets as shown in FIG. 2A. The packet isformed of a header 92 of four bytes and data section 94 of 184 bytes.

In Embodiment 3, the bit stream is detected transport packet bytransport packet and the packets of intra encoded data are recorded inthe audio areas. Transport packets are therefore detected at the packetdetector 52 from the bit stream received at the input terminal 50, andinput to the first memory 54 and the intra detector 56.

The data of the bit stream is stored in the first memory 54, packet bypacket, and is read so as to form the data of the recording data blocksshown in FIG. 2B. FIG. 2B shows the example in which five sync blocksform two transport packets, where the data length of the one sync blockis 77 bytes, as described above. In the drawing, H1 denotes a firstheader, H2 denotes a second header. Data recorded in the first header H1include identification data indicating the sync block number of eachsync block within the five sync blocks (which of the five sync blockseach sync block is), and data recorded in the second header H2 includeidentification data for indicating whether the data is video data oraudio data.

The data of the transport packet read from the first memory 54 issupplied to the third error correction encoder 130, where first andsecond headers H1 and H2 are appended to form a configuration as shownin FIG. 2B, and then error correction encoding for the video area 138 iseffected, and the data is then supplied to the digital modulator 134.

The bit stream output from the packet detector 52 is also supplied tothe intra detector 56, where judgement is made whether the data in thetransport packet is intra-encoded data or not. As described inconnection with the prior art, in the MPEG2 bit stream, if the data isintra-frame or intra-field encoded (intra-encoded), intra transportpackets are consecutively transmitted. By detecting such transportpackets consecutively transmitted, the intra transport packets areextracted, and the extracted transport packets are written in the secondmemory 58.

When the intra-encoded transport packet is read from the second memory58 in the form shown in FIG. 2B, and input to the fourth errorcorrection encoder 132, where headers H1 and H2 are appended, and errorcorrection encoding for the audio area 136 is effected, and the data isthen supplied to the digital modulator 134.

The data configuration in the audio area 136 is next described.

Referring to FIG. 17(A) to FIG. 17(D), one track consists at least of avideo area 138 and an audio area 136. The audio area 136 is formed ofdata #0 to #13 of 14 sync blocks (SBs), and each sync block is 90 byteslong (FIG. 17(B)).

As shown in FIG. 17(C), one sync block is formed of a header section 140of 5 bytes, data (C2 check code) section 142 of 77 bytes, and C1 checkcode section of 8 bytes. The header section 140 is formed of a syncpattern of 2 bytes, and identification (ID) code of 3 bytes. As shown inFIG. 18, nine sync blocks are allotted to the data region, and five syncblocks are allotted to the C2 check code region, and the data section of77 bytes is divided into an auxiliary data (AAUX data) and the audiodata.

The recording data packets formed as shown in FIG. 2B are disposed asthe AAUX data and audio data in FIG. 18, i.e., data section 142 (FIG.17(D)). Each recording data packet is formed of five sync blocks. Thedata section 142 in the audio area 136 is formed of nine sync blocks, sothat one recording data packet is recorded over a plurality of tracks.

As in the prior art example, in the digital VTR recording one frame ofvideo over ten tracks, the rate of data recorded in the audio area isabout 1.8 Mbps, and if the ATV signal rate is about 18 Mbps, the numberof bits per intra-frame is predicted to be about 1.5 Mbps, so that aboutone picture can be recorded per second.

The output of the fourth error correction encoder 132 and the output ofthe third error correction encoder 130 are input to the digitalmodulator 134, where digital modulation such as interleaved NRZI in thedata format of FIG. 17(A) to FIG. 17(D) and FIG. 18 is conducted. Themodulated data is passed via the recording amplifier 66, and recorded onoblique tracks, shown in FIG. 93, formed on the magnetic tape by meansof the rotary heads 70a and 70b.

FIG. 19 is a block diagram showing a replay system of the digital VTR ofEmbodiment 3. In the drawing, the rotary drum 68, the rotary heads 70aand 70b are identical to those in FIG. 1. Reference numeral 72 denotes ahead amplifier, 74 denotes a signal detector for detection digital datafrom the replay signal, 76 denotes a digital demodulator for performingdigital demodulation on the replay digital data, 146 denotes a thirderror correction decoder for correcting errors in the replay signal, 148denotes a fourth error correction decoder for correcting errors in thereplay signal, 82 denotes a third memory, 86 denotes a fourth memory, 88denotes a selector and 90 denotes a data output terminal.

The operation of the replay system will next be described. Still replayis started either by selection of the still mode during normal replay,or by selection in the state of halting. First, the situation where thestill mode is selected during normal replay is described.

During normal replay, the data replayed by the rotary heads 70a and 70bfrom the magnetic tape is amplified by the replay amplifier 72, andsupplied to the signal detector 74 where signal detection is performedto produce the original digital data. At the digital demodulator 76,interleaved NRZI demodulation is effected, and the replay data from thevideo areas 138 in FIG. 17(A) is supplied to the third error correctiondecoder 146 and the replay data from the audio areas is supplied to thefourth error correction decoder 148. The third error correction decoder146 and the fourth error correction decoder 148 respective correcterrors during replay, and the error corrected data from the third errorcorrection decoder 146 is written in the third memory 82 and the errorcorrected data from the fourth error correction decoder 148 is writtenin the fourth memory 86. The data selector 88 selectively outputs eitherthe output of the third memory 82 or the output of the fourth memory 86,to the output terminal 90. During normal replay, the data selector 88selects the output of the third memory 82, and the data identical to thebit stream input via the input terminal 50 is output via the outputterminal 90.

When still mode is selected during normal replay, the replay data isstopped, and data is no longer input to the third and fourth memories 82and 86. The input of the data selector 88 is then switched to select theoutput of the fourth memory 86. In this way, the still picture can beoutput via the output terminal 90. The data written in the third andfourth memories 82 and 86 include the data shown in FIG. 2B except theheaders H1 and H2, i.e., the data of the transport packets shown in FIG.2A. Only the intra-encoded data in the audio area 136 is written in thefourth memory 86, so that it is sufficient to sequentially write thedata transport packet by transport packet.

The situation where the still mode is selected from the state of haltingwill next be described. In the halting state, no correct data is storedin the third and fourth memories 82 and 86, and if the still mode isselected from this state, normal replay is conducted once, and one frameof data is stored in the fourth memory 86, and then the tape is stopped.

Next, the operation of the slow replay is described. During slow replay,the magnetic tape transport speed is lower than in the normal replay, sothat the same track is repeatedly crossed and data is replayed from thesame track for a certain number of times. By extracting the sync blockswhich are correctly demodulated by the digital demodulator 76, andinputting them into the fourth error correction decoder 148, a stillpicture can be obtained. In particular, at the tape speed of one-halfthe normal or less, all the data recorded in the audio area 136 Can bereplayed.

Embodiment 4

Description is next made of another embodiment with which deteriorationin the picture quality is small even during special replay, such as fastreplay. FIG. 20 is a block diagram showing a recording system ofEmbodiment 4. In Embodiment 4, the special replay data is recorded,being divided into the vide areas and audio areas.

In the drawings, reference numeral 150 denotes a fifth memory forreceiving the bit stream via the input terminal 50, and special replaydata, 152 denotes a special replay data generator receiving theintra-encoded transport packets and generating special replay data, and154 denotes a sixth memory for receiving the special replay data.

The special replay data generator 152 extracts the low-frequencycomponent from the packets of the intra-encoded data that have beendetected, and supplies low-frequency component to the fifth memory 150,and the subsequent high-frequency component to the sixth memory 154. Inthe prior art example, the same data is recorded 17 times in the copyareas of about 5.8 Mbps, so that the data rate of the special replaydata is 340 kbps. In this embodiment, the special replay data is alsorecorded in the audio area of about 1.8 Mbps, resulting in the copyareas of 7.6 Mbps. If the same data is recorded 17 times, the data rateof the special replay data will be about 450 kbps.

The special replay data generator 152 therefore encodes so that itsoutput is about 450 kbps, and the data for 340 kbps is supplied to thefifth memory 150 and the data for the remaining 110 kbps is supplied tothe sixth memory 154. To enable replay of the special replay data at ahigher speed, it is necessary to record the data macro block by macroblock.

FIG. 21 shows the digital video data of the macro block configuration inEmbodiment 4. Each block is formed of 8 pixels by 8 pixels in horizontaland vertical directions on the screen, i.e., 64 pixels, and four blocksof a luminance signal (Y0, Y1, Y2, Y3), and two blocks of a chrominancesignal (Cb, Cr) (the pixel density of the chrominance signal being 1/2in each of the horizontal and vertical directions, compared with thepixel density of the luminance signal), i.e., six blocks in all form avideo data of one macro block.

FIG. 22 shows coefficient of the frequency components in Embodiment 4.The pixel data of each block shown in FIG. 21 is subjected to orthogonaltransform such as DCT, and decomposed into the frequency components asshown in FIG. 22. The respective frequency components are sequentiallyscanned, starting with a DC component, and in a so-called zig-zagscanning, to perform variable-length encoding. By controlling thevariable-length encoding so that the data rate of the special replaydata is about 450 kbps, the special replay data can be generated.

It is necessary that the special replay data is encoded macro block bymacro block and partitioned into sync blocks. This is because in a fastreplay in which tracks are crossed for the scanning for replay, data isreplayed sync block by sync block.

FIG. 23 shows the disposition of the special replay data recording areasin the tracks in Embodiment 4. During replay, a process reverse to thatfor recording is followed to form special replay data. FIG. 23 shows thepositions at which the special replay data is recorded in apredetermined track pattern. Since special replay data #1 is recorded inthe audio areas, and special replay data #2 and #3 is recorded in thevideo areas, by replaying data from the audio area, special replay dataof a higher data rate can be obtained. Even if the special replay data#2 and #3 only are reproduced, special replay data having the samequality as in the prior art can be obtained. This means even if the VTRcannot pick up data from the audio areas, special replay data can bereplayed.

In Embodiment 3, description is made of the case where the data isintra-encoded frame by frame or field by field. The data mayalternatively be encoded macro block by macro block. In this case, therecording packets shown in FIG. 2B can be reconstructed for each unit ofintra-encoding, and the data may be recorded transport packet bytransport packet.

In Embodiment 4, the special replay data is recorded in both of the videareas and audio areas. The intra-encoded data may be recorded as is inboth the areas. In this case, it is possible to record a great manystill pictures for the still and slow replay. For instance, fivepictures per second can be recorded with the special replay data rate ofabout 7.6 Mbps in Embodiment 4.

Embodiment 5

FIG. 24A is a block diagram showing a recording system of a digital VTRof Embodiment 5. In the drawing, reference numeral 160 denotes a bitstream input terminal, 162 denotes an output terminal for a bit streamfor main areas, 164 denotes a low-speed fast replay data outputterminal, 166 denotes a middle-speed fast replay data output terminal,and 168 denotes a high-speed fast replay data output terminal. Referencenumeral 170 denotes a TP header analyzer for analyzing transport headersand outputting transport packets containing a transport header and intradata, 172 denotes a TP header modifying circuit for modifying thetransport headers having been separated, and 174 denotes a depacketingcircuit for converting transport packets into a bit stream, 176 denotesa header analyzer for analyzing headers such as sequence headers andpicture headers contained in the bit stream and outputting the headersand intra data, and 178 denotes a special replay data generator forgenerating special replay data for the respective replay speeds from theintra bit stream and outputting it.

Reference numeral 180 denotes a header appending circuit for appending,to the low-speed fast replay data, those of the headers extracted at theheader analyzer 176 which are necessary, 182 denotes a packeting circuitfor packeting the data into the size of a transport packet, 184 denotesa modified TP header appending circuit for appending the modifiedtransport headers, and 186 denotes a low-speed fast replay datagenerator formed of the TP header modifying circuit 172, the headerappending circuit 180, the packeting circuit 182 and the modified TPheader appending circuit 184. Reference numeral 188 denotes amiddle-speed fast replay data generator 188. Reference numeral 190denotes a high-speed fast replay data generator. The middle-speed fastreplay data generator 188 and the high-speed fast replay data generator190 have a configuration similar to that of the low-speed fast replaydata generator 186.

The operation will next be described. The bit stream received at theinput terminal 160 is output via the output terminal 162 for the bitstream for the main areas, as the data for the main areas. It is alsosupplied to the TP header analyzer 170, where headers of the transportpackets are detected from the input bit stream, and the headers areanalyzed, and if data is contained in the succeeding bit stream, thetransport packet is supplied to the depacketing circuit 174, and thetransport header is supplied to the TP header modifying circuit 172.

The depacketing circuit 174 depackets the input transport packet, andsupplies the resultant bit stream to the header analyzer 176, whereheaders such as sequence headers and picture headers in the bit streamare analyzed, and only the intra data is supplied to the special replaydata generator 178 and the headers are output to the header appendingcircuit 180.

The special replay data generator 178 generates special replay data forlow-speed fast replay, special replay data for middle-speed fast replayand special replay data for high-speed fast replay, from the input intradata. The subsequent data is identical for the respective replay speeds,so that description is made only in connection with the low-speed fastreplay data. The low-speed fast replay data output from the specialreplay data generator 178 is input to the low-speed fast replay datagenerator 186. The low-speed fast replay data is input to the headerappending circuit 180, where those of the input headers that arenecessary are appended. The output of the header appending circuit 180is supplied to the packeting circuit 182, where the low-speed fastreplay data with the necessary headers having been appended is packeted,dividing the data into the size of the transport packet. The packetedlow-speed fast replay data is supplied to the modified TP headerappending circuit 184, where modified transport headers are appended,and then output. The modified transport headers are formed by modifyingthe transport headers separated at the TP header analyzer 170, into asuitable form. In this way, the low-speed fast replay data is convertedinto the form of transport packets, and is then output via the low-speedfast replay data output terminal 164.

The description has been made of the formation of transport packets fromthe low-speed fast replay data. Similar processings are applied to themiddle-speed fast replay data and the high-speed fast replay data. Themiddle-speed fast replay data and the high-speed fast replay data outputfrom the special replay data generator 178 are respectively input to themiddle-speed fast replay data generator 188 and the high-speed fastreplay data generator 190, and headers and modified headers areappended, and output in the form of transport packets via themiddle-speed fast replay data output terminal 166 and the high-speedfast replay data output terminal 168.

Further description of the special replay data generator 178 will nextbe given.

FIG. 24B is a block diagram showing an example of the special replaydata generator 178. In the drawing, reference numeral 192 denotes aninput terminal for receiving a bit stream of intra data, 194 denotes avariable-length decoder for forming low-speed special replay data, 196denotes a variable-length decoder for forming middle-speed specialreplay data, and 198 denotes a variable-length decoder for forminghigh-speed special replay data. Reference numerals 200, 202 and 204denote counters. Reference numerals 206, 208 and 210 denote dataextractors for low-speed fast replay data, middle-speed fast replaydata, and high-speed fast replay data, respectively.

Reference numeral 212 denotes an EOB appending circuit for appending EOB(end of block) code to the low-speed fast replay data, 214 denotes anEOB appending circuit for appending EOB code to the middle-speed fastreplay data, and 216 denotes an EOB appending circuit for appending EOBcode to the high-speed fast replay data. Reference numeral 218 denotesan output terminal for low-speed fast replay data, 220 denotes an outputterminal for middle-speed fast replay data, and 222 denotes an outputterminal for high-speed fast replay data.

The operation of the special replay data generator 178 (FIG. 24B) willnext described. The variable-length decoder 194 variable-length decodesthe input bit stream. On the basis of the decoding, the counter 200counts the number of the decoded DCT coefficients, and outputs theresult to data extractor 206 extracts the bits stream corresponding tothe predetermined number of DCT coefficients, from the input bit stream,at a predetermined timing, on the basis of the input from the counter200. The counter 202 and the data extractor 208, and the counter 204 andthe data extractor 210 perform similar operation. The data extractor 206extracts the low-speed fast replay data from the input bit stream, thedata extractor 208 extracts the middle-speed fast replay data from theinput bit stream, and the data extractor 210 extracts the high-speedfast replay data from the input bit stream. The extracted low-speed fastreplay data is supplied to the EOB appending circuit 212 where EOB codesare appended, and then output as the low-speed fast replay data via theoutput terminal 218. The extracted middle-speed fast replay data issupplied to the EOB appending circuit 214 where EOB codes are appended,and then output as the middle-speed fast replay data via the outputterminal 220. The extracted high-speed fast replay data is supplied tothe EOB appending circuit 216 where EOB codes are appended, and thenoutput as the high-speed fast replay data via the output terminal 222.

The timings at which the data is extracted at the respective dataextractors may be identical to each other, or may be different. If theyare different, the number of DCT coefficients within one video block tobe recorded (the unit with which the orthogonal transform is performedat the encoding means) differs. Since the special replay area wherespecial replay data is recorded is limited as will be described later,if the special replay area is of the same areas (size), increase in thenumber of the DCT coefficients of one video block requires more specialreplay areas for recording, and the refreshing of the screen duringreplay is slow. However, the picture quality is good. Decision on thetiming for extraction is therefore made by trade-off between the delayin refreshing and the picture quality.

FIG. 25 is a block diagram showing a sync block forming circuit.

In FIG. 25, reference numeral 224 denotes an input terminal for a bitstream for main areas, 226 denotes an input terminal for low-speed fastspecial replay data, 228 denotes an input terminal for middle-speed fastspecial replay data, 230 denotes an input terminal for high-speed fastspecial replay data. The input terminals 224, 226, 228 and 230 arerespectively connected to the output terminals 162, 164, 166 and 168 inFIG. 24A. Reference numeral 232 denotes an SB format circuit forconverting the input data and the bit stream into a sync block format.Reference numeral 234 denotes an SB output terminal for outputting SBdata.

The synthesis of the bit stream for the main areas and the specialreplay data for the respective fast will next be described withreference to FIG. 25. The data and the bit stream received at the inputterminals 224 to 230 are input to the SB format circuit 232, where datato be recorded in the respective sync block are selected for each trackand for each sync block. A header is appended to each sync block ofdata, and the sync blocks within a track are formed to thereby form thepredetermined pattern as described later, and the resultant data isoutput via the SB output terminal 234.

The operation of the SB format circuit 232 will next be described. Inthis embodiment, the drum may be of any of 1 ch×2, 2 ch×1 and 2 ch×2configurations. However, two azimuth angles are provided, and the headhaving one azimuth angle is called an A-channel head, and the headhaving the other azimuth angle is called B-channel head.

FIG. 26A to FIG. 26F are diagrams showing the configurations of thespecial replay data recording areas according to Embodiment 5. In thedrawing, reference numeral 242 denotes A-channel low-speed fast replayrecording area for recording low-speed fast replay data by means of anA-channel head, 244 denotes a B-channel low-speed fast replay recordingarea for recording low-speed fast replay data by means of a B-channelhead, 246 denotes A-channel middle-speed fast replay recording area forrecording low-speed fast replay data by means of an A-channel head, 248denotes a B-channel low-speed fast replay recording area for recordinglow-speed fast replay data by means of a B-channel head, 250 denotesA-channel high-speed fast replay recording area for recording low-speedfast replay data by means of an A-channel head, and 252 denotes aB-channel high-speed fast replay recording area for recording low-speedfast replay data by means of a B-channel head. The B-channel data isthat obtained when 2 ch×2 drum configuration is used. Compared withother drum configurations, in the case of the 2 ch×2 drum configuration(assuming that the replay speed is identical), the number of times thehead crosses the track is larger, and the number of sync blocksreproduced per track is small. As a result, it is necessary tosupplement the data of special replay data recording areas from whichthe data is not produced by the A-channel head.

The special replay data recording areas for the B-channel head areprovided for the above-described reason. The B-channel low-speed fastreplay data recording areas 244 supplement the A-channel low-speed fastreplay data recording areas 242, the B-channel middle-speed fast replaydata recording areas 248 supplement the A-channel low-speed fast replaydata recording areas 246, and the B-channel high-speed fast replay datarecording areas 250 supplement the A-channel high-speed fast replay datarecording areas 252. With regard to the size of the respective areas,since the same size of the areas for the A- and B-channels can be usedin the 2 ch×2 drum configuration, and data can be replayed from aboutdouble the areas by means of the A-channel head in other drumconfigurations, the ratio of the A-channel special replay area to theB-channel special replay area is 2:1.

The numbers 1 to 14 allotted to the respective blocks in FIG. 26A toFIG. 26F indicate the content of the data. That is identical numberdenotes identical data. The data at the upper and lower ends of theA-channel special replay areas and also form the data of the B-channelspecial replay areas. The reason is as explained above. Each block isformed of m sync blocks (m being a natural number).

FIG. 27 shows the disposition of the special replay data recording areasin the tracks. In this recording format, as in Embodiment 1, the specialreplay data recording areas are repeated at a period of four tracks. Thespecial replay data recording areas corresponding to the respectivereplay speeds are provided in four tracks 98, 100, 102 and 104 of oneperiod. In the drawing, the track 98 is a first track recorded by anA-channel head, the track 100 is a second track recorded by a B-channelhead, the track 102 is a third track recorded by the A-channel head, thetrack 104 is a fourth track recorded by the B-channel head. The first tofourth tracks 98 to 104 form a unit. f0, f1 and f2 represent pilotsignals for identifying the respective tracks. The pilot signal f1 is asignal of a frequency, denoted by f1, superimposed with the digitalsignal recorded on the track. The pilot signal f2 is a signal of anotherfrequency, denoted by f2, different from f1, and superimposed with thedigital signal recorded on the track. The pilot signal f0 is actually inthe form of absence of superimposed signals f1 and f2. The areas otherthan the areas 242 to 252 are used as main areas for recording data fornormal replay. Data from the areas for special replay can be reproducedby one scan of a head whatever is the configuration of the drum. In thecase of the 2 ch×1 or 1 ch ×2 drum configuration, the special replaydata in concentrated areas on one track can be reproduced by one scan ofa head. In the case of the 2 ch×2 drum configuration, the special replaydata can be formed from adjacent tracks. By recording the special replaydata collectively, in concentrated areas as shown in FIG. 27, it ispossible to remove the effects of non-linearity of the tracks.

The pilot signals can be superimposed on the digital data at a modulator502, shown in FIG. 28, provided in front of a recording amplifier 503,from which recording signals are supplied to a recording head 504 forrecording the signals on the magnetic tape 505. The superimposition canbe achieved by dividing the code sequence into units of 24 bits, andadding one bit to the head of each unit of 24 bits, and selectivelysetting the additional bit to "0"or "1" to thereby vary the DSV (digitalsum variation).

It should be noted, the system shown in FIG. 1, FIG. 16 and FIG. 20 alsois provided with a modulator in front of the recording amplifiers 88,but such a modulator is not shown for simplicity of illustration.

FIG. 29 is a diagram showing a recording format on tracks in Embodiment5. The unit of four tracks shown in FIG. 27 is repeated, and recordingis made on the repeated units, to form the recording pattern. In therecording pattern shown in FIG. 29, four-time speed is set as thelow-speed fast replay speed, eight-time speed is set as the middle-speedfast replay speed, and 16-time speed is set as the high-speed fastreplay speed. The data for four-time speed is repeatedly recorded overtwo units of four tracks, the data for the eight-time speed isrepeatedly recorded over four units of four tracks, and the data for the16-time speed replay is repeatedly recorded over eight units of fourtracks. To generalize, the data for the (M×i)-time speed replay isrepeatedly recorded over 2×i units of four tracks, where M is four inthe illustrated example, and i=1, 2 . . . n.

By forming the recording pattern as described above, the effects of anynon-linearity of tracks can be minimized. Moreover, because dedicatedareas are provided for the respective fast replay speeds, the refreshingand the picture quality can be set for the respective fast replayspeeds.

Embodiment 6

Embodiment 6 relates to a different configuration of a special replaydata generator 178. The special replay data generator 178 in Embodiment5 was in the form shown in FIG. 24B. The invention is not limited tosuch a configuration, but the configuration shown in FIG. 30 may beused.

Referring to FIG. 80, the differences from the special replay datagenerator 178 shown in FIG. 24B will be described.

Reference numeral 260 denotes a variable length decoder forvariable-length decoding the input bit stream, 262 denotes a counter,264 denotes a data extractor for extracting low-speed data, 266 denotesa data extractor for extracting middle-speed data, and 268 denotes adata extractor for extracting high-speed data. Reference numerals 192,212, 214, 216, 218, 220 and 222 in FIG. 30 denote members identical tothose in FIG. 24B.

The operation of the special replay data generator in Embodiment 6 willnext be described. The intra data received at the input terminal 192 isinput to the variable-length decoder 260, and the data extractors 264,266 and 268. The variable-length decoder 260 performs variable-lengthdecoding on the bit stream. The counter 262 counts the number of DCTcoefficients obtained as a result of the decoding, and the count valueis supplied to the data extractors 264, 266 and 268. The data extractor262 extracts the data at a timing predetermined according to the input.Similarly, the data extractor 266 and the data extractor 268respectively extract data at timings predetermined independently of eachother. The extracted data is supplied to the EOB appending circuits212,214 and 216, where EOB code is appended, and then output via theoutput terminals 218, 220 and 222. By forming the circuit as describedabove, the special replay data similar to that of FIG. 24B can begenerated.

Embodiment 7

FIG. 31 is a block diagram showing an example of sync block formingcircuit of Embodiment 7. In Embodiment 7, a configuration different fromthe sync block forming circuit of Embodiment 5 (FIG. 25) is used tosynthesize the bit stream for the main areas and the special replay datafor the respective fast replay speeds.

In FIG. 31, reference numeral 224 denotes an input terminal forreceiving the main area bit stream, 226 denotes an input terminal forreceiving special replay data for low-speed, 228 denotes an inputterminal for receiving special replay data for middle-speed, and 230denotes an input terminal for receiving special replay data forhigh-speed. Reference numeral 232 denotes an SB format circuit forconverting the input data and bit stream into the format of sync blocks,270 denotes an error correction encoder, and 234 denotes an outputterminal for outputting the SB data.

Referring to FIG. 31, the operation for synthesizing the main stream bitstream and the special replay data for the respective fast replay speedswill next be described. The data and bit stream input via the inputterminals 224 to 230 are input to the SB format circuit 232, where thedata to be recorded in the respective sync blocks is selected, from therespective inputs, for each of the tracks and for each of the syncblocks. A header is appended to each of the sync block of data, and thesync blocks in each track are configured so as to form the predeterminedpattern, to be described later, and a second parity (C1 code) formed ofdigital data, and a third parity (C2 code) formed of a plurality ofitems of digital data extending across a sync bit, are appended, and theresult is output via the SB output terminal 234.

The configuration of the special replay data recording areas, and thedisposition of the special replay data recording areas, and therecording format on the tracks may be identical to those described withreference to FIG. 26A to FIG. 29 in connection with Embodiment 5.

Description will next be made as to in what format, the transportpackets are recorded in fixed areas, such as sync blocks.

FIG. 32 is a diagram showing an example of data packet according toEmbodiment 7. It shows an example for the case where two transportpackets are recorded over five sync blocks. In the drawings, referencenumeral 300 denotes a sync of a sync block 0 (SB0), 301 denotes a syncof a sync block 1 (SB1), 302 denotes a sync of a sync block 2 (SB2), 303denotes a sync of a sync block 3 (SB3), and 304 denotes a sync of a syncblock 4 (SB4). Reference numeral 305 denotes ID of SB0, 306 denotes IDof SB1, 307 denotes ID of SB2, 308 denotes ID of SB3, and 309 denotes IDof SB4. Reference numeral 310 denotes a header appended to SB0, 311denotes a header appended to SB1, 312 denotes a header appended to SB2,313 denotes a header appended to SB3, and 314 denotes a header appendedto SB4. Reference numeral 315 denotes a transport header of thetransport packet A, 316 denotes data of the transport packet A, 317denotes a transport header B of the transport packet B, and 318 denotesdata of the transport packet B. Reference numeral 319 denotes a dummyarea.

Reference numeral 320 denotes a sync parity generated from the digitaldata succeeding ID 305. Reference numeral 321 denotes a sync paritygenerated from the digital data succeeding ID 306. Reference numeral 322denotes a sync parity generated from the digital data succeeding ID 307.Reference numeral 323 denotes a sync parity generated from the digitaldata succeeding ID 308. Reference numeral 324 denotes a sync paritygenerated from the digital data succeeding ID 309. Reference numeral 330denotes a C1 check code which is a second parity appended at the errorcorrection encoder 270. Reference numeral 331 denotes a C2 check codewhich is a third parity appended at the error correction encoder 270.

Description is made of SB0. ID 305 and header 310 contain an address foridentifying the particular sync block within the five sync blocks, asignal indicating whether normal replay data or special replay data isrecorded, a signal for identifying the speed where the special replaydata is recorded, a signal for indicating the identity of data forseveral units needed since identical special replay data is recorded forseveral units and discriminating from the special replay data recordedin the succeeding several units, and a signal for identifying theassembly of the five sync blocks, for each unit of the five blocks, anda signal indicating whether the central part of the screen (picture) ofan intra-frame or intra-field.

In Embodiment 7, address identifying each sync block within the group offive sync blocks and a signal indicating whether normal replay data orspecial replay data is contained are recorded in ID 305, and theremainder is recorded in the header 310 disposed after the ID, for eachsync block. The ID 305 records the necessary signals among the signalsstipulated by the SD specification.

That is, ID 305 contains a parity of the ID signal which is a firstparity. This parity is for checking whether the ID signal containing theparity is correct, and its size is one byte. The C1 check code 330 whichis the second parity is of eight bytes, and the C2 check code which isthe third parity is of 11 bytes. The fourth parity is the sync parity320 which is of one byte.

SB1, SB2, SB3 and SB4 record an ID and a header, like SB0. In thisembodiment, the size of the sync block is 82 bytes (excluding the C1area), the size of each sync is 2 bytes, the size of each ID is 3 bytes,and the size of each header is one byte. The size of each sync parity isone byte. The size of the transport packet is 187 bytes (as the signalof one byte which can be appended at the time of replay is removed fromthe transport header at the time of recording). Accordingly, twotransport packets (187×2=374 bytes) can be recorded in the data regionsof five sync blocks (76×5=300 bytes). The remaining one byte forms thedummy area 319 in FIG. 32. In this way, two transport packets can berecorded in five sync blocks. By recording, at the tail of the syncblock, sync parities generated from the digital data contained in thesync block, it is possible to provide a format permitting detection ofwhether the digital data contained in the sync block is erroneous.

Embodiment 8

FIG. 33 is diagram showing a recording format on tracks of a digital VTRaccording to Embodiment 8. In the drawings, four tracks form one unit,and a pattern formed of four tracks is repeated.

That is, of the 135 sync blocks of sync block Nos. 21 to 155 of therespective tracks, the data for +8-time speed replay and -6-time speedreplay is recorded in the area b0 formed of the sync blocks Nos. 96 to115 in the first track of the group of four tracks, and the area b1formed of the sync blocks Nos. 96 to 106 in the second track of thegroup of four tracks. The data for +2-time speed replay, +4-time speedreplay and -2-time speed replay is recorded in the area a0 formed of thesync blocks Nos. 104 to 143 in the third track of the group of fourtracks, and the area a1 formed of the sync blocks Nos. 109 to 128 in thefourth track of the group of four tracks. The data for +16-time speedreplay and -14-time speed replay is recorded in the area c0 formed ofthe sync blocks Nos. 72 to 81 in the third track of the group of fourtracks, and the area cl formed of the sync blocks Nos. 70 to 79 in thefourth track of the group of four tracks.

The data recorded in the areas a1, b1 and c1 are identical to the datarecorded in the both end parts of the areas a0, b0 and c0, respectively,and is used to supplement when the data at the end parts of the areasa0, b0 and c0 is not obtained. With regard to the data for +2-time speedreplay, +4-time speed replay and -2-time speed replay, identical data isrecorded in two tracks. With regard to the data for +8-time speed replayand -6-time speed replay, identical data is recorded in four tracks.With regard to the data for +16-time speed replay and -14-time speedreplay, identical data is recorded in eight tracks. In the remainingvideo areas, normal replay data is recorded, and the sync block numberis recorded in each sync block. As in the SD mode, pilot signals fortracking control are recorded in the respective tracks, in the order off0, f1, f0 and f2, in superimposition with the digital signal.Accordingly, the pilot signal f0 is recorded in the first and thirdtracks, the pilot signal f1 is recorded in the second track, and thepilot signal f2 is recorded in the fourth track.

The configuration of the head used for the recording or replay may forexample be as shown in FIG. 5A to FIG. 5C, in which one head each isdisposed at opposite positions 180° apart on the drum, two heads aredisposed at positions close to each other on the drum, or two heads eachare disposed at positions opposite positions 180° apart on the drum. Inthe following description, the 2ch×1 configuration in which two headsare disposed at positions close to each other on the drum will be takenas an example. The head having the same azimuth as the first and thirdtracks in which the pilot signal f0 is recorded is called a first head,while the head having the same azimuth as the second and fourth tracksin which the pilot signals f1 and f2 are recorded is called a secondhead.

During fast replay, the specific scanning trace is followed depending onthe replay speed to reproduce the desired replay data. The method oftracking will be described.

FIG. 34 is a schematic block diagram showing the configuration of thecapstan servo system. In the drawing, reference numeral 340 denotes acapstan motor, 342 denotes a FG (frequency generator) section forgenerating FG signal of a frequency corresponding to the rotary speed ofthe capstan motor 340, 344 denotes a speed detector for detecting thespeed error of the capstan motor 340, by detecting the period of the FGsignal, 346 denotes a tracking error detector for detecting the trackingerror, 348 denotes an adder for adding the outputs of the speed detector344 and the tracking error detector 346, and 350 denotes a driver fordriving the capstan motor in accordance with the output of the adder348.

FIG. 35 is a diagram showing an example of configuration of the trackingerror detector 346 in FIG. 34. In the drawing, reference numeral 352denotes a first head, 354 denotes a head amplifier, 356 and 358respectively denote BPFs (bandpass filters) having central frequenciesf1 and f2, respectively, 360 and 362 denote detectors, 364 and 366denote sample-hold circuits, and 368 denotes a sampling pulse generatorfor generating sampling pulses for the sample-hold circuits 364 and 366.Reference numerals 370 and 372 denotes selectors for selecting theoutputs of the sample-hold circuits 364 and 366. Reference numeral 374denotes a controller for controlling the selectors 370 and 372.Reference numeral 376 denotes a subtractor for performing subtraction onthe outputs of the selectors 370 and 372.

The replay operation of the digital VTR of Embodiment 8 will next bedescribed with reference to FIG. 36 to FIG. 42.

FIG. 36 shows the head scanning traces. During +2-time speed replay, thetarget speed for the speed detector 344 is set at twice the speed duringrecording, and the tape speed is controlled to be the double speed. Bythe function of the tracking error detector 346, the tracking control iseffected. The signal reproduced by the first head 352 at the +2-timespeed is amplified by the head amplifier 354, and the frequencycomponents of the pilot signals f1 and f2 are extracted by the BPFs 356and 358. The amplitudes of the f1 and f2 components are substantiallyproportional to the amount over which the first head 352 is on thetrack. The pilot signals extracted by the BPFs 356 and 358 areenvelope-detected at the detectors 360 and 362, and then sample-held atthe sample-hold circuits 364 and 366. The timing for the sample-holdingis determined by the sample-hold pulse from the sampling pulse generator368.

In the case of +2-time speed replay, the sampling pulse generator 368 ismade to generate one pulse per drum rotation such that the samplingtakes place when the first head is at about the sync block No. 124 atthe center of the area a0 formed of the sync block Nos. 104 to 143 where+2-time speed replay data is recorded. In the case of +2-time speedreplay, the selector 370 is made to select the output of the sample-holdcircuit 364 and the selector 372 is made to select the output of thesample-hold circuit 366, on the basis of the control signal from thecontroller 374. Accordingly, the output of the sample-hold circuit 364is input to the "+" input terminal of the subtractor 376, while theoutput of the sample-hold circuit 366 is input to the "-" input terminalof the subtractor 376. The output of the subtractor 376 is a trackingerror signal corresponding to the {(pilot signal f1 component)-(pilotsignal f2 component)}.

If the head is toward the fourth track (of the four tracks), rather thanthe third track in the lateral direction of the tracks when the firsthead 352 is at about the sync block No. 124 in the longitudinaldirection of the track, the pilot signal f2 component is larger than f1component, and the tracking error signal will be small. This trackingerror signal is output from the tracking error detector 346, and addedto the output of the speed detector 344 at the adder 348. By theresultant output of the driver 350, the capstan motor 340 isdecelerated, to retard the tracking phase. Conversely, if the head istoward the second track (of the four tracks), rather than the thirdtrack in the lateral direction of the tracks when the first head 352 isat about the sync block No. 124 in the longitudinal direction of thetrack, the pilot signal f2 component is smaller than f1 component, andthe tracking error signal will be large. This tracking error signal isoutput from the tracking error detector 346, and added to the output ofthe speed detector 344 at the adder 348. By the resultant output of thedriver 350, the capstan motor 340 is accelerated, to advance thetracking phase.

In this way, the tracking is so controlled that the pilot signal f1 andf2 components are equal so that the first head scans the center, in thelateral direction of the tracks, of the third track (of the four tracks)when the first head 352 is at about the sync block No. 124 in thelongitudinal direction of the track. In the center of the first track(of the four tracks) the pilot signal f1 and f2 components are equal toeach other, but as the front-rear relationship between f1 and f2 isopposite, the polarity of the tracking error signal will be opposite,and the tracking is not stabilized in this position, but is pulled intothe center of the third track. That is, if the tracking is shiftedtoward the fourth track (of the preceding group of four track), theoutput of the driver 350 will decelerate the capstan motor 340 to retardthe tracking phase, to thereby bring the head to the third track in thepreceding group of four tracks while if the tracking is shifted towardthe second track (next to the first group (of the same group of fourtracks), the output of the driver 350 will further accelerate thecapstan motor 340 to advance the tracking phase, to thereby bring thehead to the third track (of the same group of four tracks). When thefirst head 352 scans the center of the third track, the second headsscans the center of the fourth track. In this way, the +2-time speedreplay data in the areas a0 and al in every group of four tracks isreplayed.

FIG. 37 and FIG. 38 respectively show head scanning traces at the timeof +4-time speed replay and +16-time speed replay, respectively. During+4-time speed replay and 16-time speed replay, the target speed of thespeed detector 344 is set four-times and 16 times the recording speed,respectively, and by the function of the speed control system, the tapespeed is controlled to be the +4-time speed and +16-time speed,respectively. The operation for producing the tracking error signal issimilar to that described in connection with the case of +2-time speedreplay. That is, in the case of +4-time speed replay, the tracking errordetector 346 outputs the tracking error signal corresponding to the{(pilot signal f1 component) (pilot signal f2 component)} when the firsthead is at about the sync block No. 124 at the center of the area a0formed of the sync blocks Nos. 104 to 143 where the +4-time speed replaydata is recorded. In the case of +16-time speed replay, the trackingerror detector 346 outputs the tracking error signal corresponding tothe (pilot signal f1 component)-(pilot signal f2 component) when thefirst head is at about the sync block No. 77 at the center of the areac0 formed of the sync blocks Nos. 72 to 81 where the +16-time speedreplay data is recorded.

In accordance with this tracking error signal, the tracking is socontrolled that the pilot signal f1 and f2 components are equal so thatthe first head scans the center, in the lateral direction of the tracks,of the third track (of the four tracks) when the first head 352 is atabout the center, in the longitudinal direction of the track, of thearea where the fast replay data for the respective speeds is recorded.In this way, +4-time speed replay data in the area a0 and the area a1 ofevery eight tracks, or +16-time speed replay data in the area c0 and thearea c1 of every 32 tracks is reproduced. In the case of +4-time speedreplay, the head scanning trace follow either of two patterns, but asthe same data is recorded on two tracks, the same data is reproducedwhich ever of the scanning trace) patterns is followed. This alsoapplies to other replay speeds.

The +16-time speed replay will next be described. FIG. 39 shows headscanning traces at the time of +8-time speed replay. During +8-timespeed replay, the target speed of the speed detector 344 is set at eighttimes the recording speed, and by the function of the speed controlsystem, the tape speed is controlled to be the eight-time speed. By thefunction of the tracking error detector 346, the tracking is controlled.At +8-time speed, the signal picked up by the first head 352 isamplified by the head amplifier 354, and pilot signal f1 and f2components are extracted by the BPFs 356 and 358, respectively, andenvelope-detected by the detectors 360 and 362, respectively, and thensample-held by the sample-hold circuits 364 and 366, respectively. Thesampling timing is determined by the sampling pulses from the samplingpulse generator 368. In the case of the +8-time speed replay, thesampling pulse generator 368 is made to generate one pulse per drumrotation such that the sampling takes place when the first head is atabout the sync block No. 106 at the center of the area b0 formed of thesync block Nos. 96 to 115 where +8-time speed replay data is recorded.In the case of +8-time speed replay, the selector 370 is made to selectthe output of the sample-hold circuit 366 and the selector 372 is madeto select the output of the sample-hold circuit 364, on the basis of thecontrol signal from the controller 374. Accordingly, the output of thesample-hold circuit 364 is input to the "-" input terminal of thesubtractor 376, while the output of the sample-hold circuit 366 is inputto the "+" input terminal of the subtractor 376. The output of thesubtractor 376 is a tracking error signal corresponding to the {(pilotsignal f2 component)-(pilot signal f1 component)}.

On the basis of this tracking error signal, the tracking is socontrolled that the pilot signal f1 and f2 components are equal, and thefirst head 352 scans the center, in the lateral direction of the tracks,of the first track (of the four tracks) when the first head 352 is atabout the sync block No. 106 in the longitudinal direction of the track.In this way, the +8-time speed replay data in the area b0 and b1 ofevery 16 tracks is reproduced. FIG. 40, FIG. 41 and FIG. 42 respectivelyshow head scanning traces at the time of -2-time speed replay, -6-timespeed replay, and -14-time speed replay. In the case of reverse fastreplay, the tape is transported in the reverse direction at therespective fast replay speeds, and the tracking control in -2-time speedreplay, -6-time speed replay, and -14-time speed replay, is effected inthe same way as in +4-time speed replay (for the -2-time speed replay),in +8-time speed replay (for the -6-time speed replay), and in +16-timespeed replay (for the -14-time speed replay), respectively. However,since, in the reverse fast replay, the tape transport direction isopposite to forward fast replay, it is necessary to reverse the polarityof the tracking error signal (as compared with the case for forward fastreplay), and the positions of the selectors 370 and 372 are opposite tothose for the corresponding forward fast replay. That is, the positionsof the selectors 370 and 372 in the -2-time speed replay is opposite topositions of the selectors in the +4-time speed replay; the positions ofthe selectors 370 and 372 in the -6-time speed replay is opposite topositions of the selectors in the +8-time speed replay; and thepositions of the selectors 370 and 372 in the -14-time speed replay isopposite to positions of the selectors in the +16-time speed replay.

Embodiment 9

In Embodiment 8, the sampling timing pulses for the sample-hold circuits364 and 366 are generated at the sampling pulse generator 368 inaccordance with the signal indicative of the drum rotation phase. Theaccuracy of the sampling timing can be improved in the sync block numberin the replay signal. This method will next be described.

FIG. 43 shows an example of configuration of a tracking error detector.The schematic illustration of the capstan servo system is identical tothat illustrated in FIG. 34. The configuration of the tracking errordetector shown in FIG. 43 is similar to that of FIG. 34, but a secondsampling pulse generator 382 and a selector 380 are added. The selector380 selectively connects the outputs of the sampling pulse generators368 and 382 to the sample-hold circuits 364 and 366. The second samplingpulse generator 382 processes the replay signal output from the headamplifier 354 and detects the sync block number. The second samplingpulse generator 354 generates a sampling pulse when it detects the syncblock number of the sync block at the center of the area formed of thesync blocks where the fast data for the selected replay speed isrecorded, i.e., at the sync block No. 124 at the center of the syncblock Nos. 104 to 143 (a0) where +2-time speed replay data and +4-timespeed replay data are recorded, during +2-time speed replay or +4-timespeed replay, the sync block No. 106 at the center of the sync blockNos. 96 to 115 (b0) where +8-time speed replay data is recorded, during+8-time speed replay, and the sync block No. 77 at the center of thesync block Nos. 72 to 81 where +16-time speed replay data is recorded,during +16-time speed replay.

The operation for detecting the tracking error will next be described.Except that the manner of generating the sampling pulses is different,the operation is identical to that of Embodiment 8. Accordingly, themanner of sampling pulse generation will be described. When the fastreplay is just started, and the tracking control is not in pull-instate, the selector 380 selects the output of the first sampling pulsegenerator 368, and the sampling pulse generated from the signalindicative of the drum rotation phase is supplied to the sample-holdcircuits 364 and 366. When the system is brought into a state in whichthe tracking control is nearly in pull-in state, and the replay signalfrom the areas where the required fast replay signal is recorded isobtained, and sampling pulses are generated from the second samplingpulse generator 388, then the selector 380 selects the output of thesecond sampling pulse generator 382, and each time the predefined syncblock is detected, a sampling pulse is supplied to the sample-holdcircuits 364 and 366.

The switching operation of the selector 380 can be controlled by acontrol means, such as a microcomputer, not shown. For instance,judgement is made whether a sampling pulse is output from the secondsampling pulse generator 382 is generated during each ration of thedrum, and if a sampling pulse is output from the second sampling pulsegenerator 382 during each rotation of the drum, then the selector 380 isswitched to select the output of the second sampling pulse generator382. Otherwise, the selector is switched to select the output of thefirst sampling pulse generator 368.

In the description of Embodiments 8 and 9, the drum configuration is 2ch×1 type in which two heads provided at positions close to each other.The drum configuration may alternatively be of the 1 ch×2 type in whichtwo heads are at opposite positions, 180° apart on the drum, asdescribed next.

FIG. 44 shows head scanning traces during +4-time speed replay in amodification of Embodiments 8 and 9. In this case, the head scanningtraces of the first head is identical to those of the 2 ch×1configuration, while the head scanning traces of the second head isdifferent. The fast replay is effected using only the data in the areasa0, b0 or c0 picked up by the first head.

The above-described tracking control can be achieved even in the 2 ch×2system configuration in which two heads each are disposed at oppositepositions, 180° apart. FIG. 45 shows head scanning traces during +4-timespeed replay in such a system configuration. In comparison with the casewhere two heads are at positions on the drum close to each other, theangle of inclination of the head scanning traces is different, but thedata at both ends of the areas a0, b0 and c0 which cannot be reproducedis supplemented by the data at the areas a1, b1 and c1, so that the fastreplay signal can be obtained in a similar manner.

In connection with Embodiments 8 and 9, description is made for the caseof +2-, +4-, +8-, +16-, -2-, -6- and -14-time speed replays. But thereplay may be at any of +4N- or (-4N+2)-time speed (N being a positiveinteger), and the fast replay data may be recorded in positions otherthan those shown, as far as the data is collectively recorded.

In Embodiments 8 and 9, the pilot signals f1 and f2 of two differentfrequencies and f0 where none of them is recorded, are used as the pilotsignals for tracking. Alternatively, four types of pilot signals may beused, as in 8 mm VTR, for tracking control, and yet similar result willbe obtained.

Embodiment 10

In Embodiment 10, replay of a magnetic tape (FIG. 29) having beenrecorded as in Embodiment 5 will be described. In Embodiment 5, thelow-speed fast replay speed was set at a four-time speed, themiddle-speed fast replay speed was set at a eight-time speed and thehigh-speed fast replay speed was set at a 16-time speed. In Embodiment10, the replay at the respective fast replay speeds will be described.

FIG. 46 shows the rotary head scanning traces followed during four-timespeed fast replay of the special replay data in the recording format,using a 1 ch×2 head system, according to Embodiment 10. The arrowsindicate the head scanning traces. The servo is locked in the area wherefour-time speed replay data is recorded. Since two units of thefour-time speed replay data is recorded repeatedly, one of the two unitsis scanned by the A-channel head, while the other is scanned by theB-channel head. In this way, it is possible to reproduce the four-timespeed replay data recorded using the A-channel head.

FIG. 47 shows the rotary head scanning traces followed during four-timespeed fast replay of the special replay data in the recording format,using a 2 ch×1 head system, according to Embodiment 10. The arrowsindicate the head scanning traces. The servo is locked in the area wherefour-time speed replay data is recorded. Since two units of thefour-time speed replay data is recorded repeatedly, one of the two unitsis scanned by either of the 2 ch heads. In this way, it is possible toreproduce the four-time speed replay data recorded using the A-channelhead.

FIG. 48 shows the rotary head scanning traces followed during four-timespeed fast replay of the special replay data in the recording format,using a 2 ch×2 head system, according to Embodiment 10. The arrowsindicate the head scanning traces. The servo is locked in the area wherefour-time speed replay data is recorded. Since two units of thefour-time speed replay data is recorded repeatedly, one of the two unitsis scanned by either of the 2 ch heads. However, for the reasondescribed in connection with Embodiment 5, not all the four-time speedreplay data can be reproduced by the A-channel head alone. However, bysynthesis with the four-time speed replay data recorded by the B-channelhead and picked up the B-channel head, the replay is possible.

FIG. 49 shows the rotary head scanning traces followed during eight-timespeed fast replay of the special replay data in the recording format,using a 1 ch×2 head system, according to Embodiment 10. The arrowsindicate the head scanning traces. The servo is locked in the area whereeight-time speed replay data is recorded. Since four units of theeight-time speed replay data is recorded repeatedly, one of the fourunits is scanned by the A-channel head, while another of the four unitsis scanned by the B-channel head. In this way, it is possible toreproduce the eight-time speed replay data recorded using the A-channelhead.

FIG. 50 shows the rotary head scanning traces followed during eight-timespeed fast replay of the special replay data in the recording format,using a 2 ch×1 head system, according to Embodiment 10. The arrowsindicate the head scanning traces. The servo is locked in the area whereeight-time speed replay data is recorded. Since four units of theeight-time speed replay data is recorded repeatedly, one of the fourunits is scanned by either of the 2 ch heads. In this way, it ispossible to reproduce the eight-time speed replay data recorded usingthe A-channel head. FIG. 51 shows the rotary head scanning tracesfollowed during eight-time speed fast replay of the special replay datain the recording format, using a 2 ch×2 head system, according toEmbodiment 10. The arrows indicate the head scanning traces. The servois locked in the area where eight-time speed replay data is recorded.Since four units of the eight-time speed replay data is recordedrepeatedly, one of the four units is scanned by either of the 2 chheads. However, for the reason described in connection with Embodiment5, not all the eight-time speed replay data can be reproduced by theA-channel head alone. However, by synthesis with the eight-time speedreplay data recorded by the B-channel head and picked up the B-channelhead, the replay is possible.

FIG. 52 shows the rotary head scanning traces followed during 16-timespeed fast replay of the special replay data in the recording format,using a 1 ch×2 head system, according to Embodiment 10. The arrowsindicate the head scanning traces. The servo is locked in the area where16-time speed replay data is recorded. Since eight units of the 16-timespeed replay data is recorded repeatedly, one of the eight units isscanned by the A-channel head, while another of the eight units isscanned by the B-channel head. In this way, it is possible to reproducethe 16-time speed replay data recorded using the A-channel head.

FIG. 53 shows the rotary head scanning traces followed during 16-timespeed fast replay of the special replay data in the recording format,using a 2 ch×1 head system, according to Embodiment 10. The arrowsindicate the head scanning traces. The servo is locked in the area where16-time speed replay data is recorded. Since eight units of the 16-timespeed replay data is recorded repeatedly, one of the eight units isscanned by either of the 2 ch heads. In this way, it is possible toreproduce the 16-time speed replay data recorded using the A-channelhead.

FIG. 54 shows the rotary head scanning traces followed during 16-timespeed fast replay of the special replay data in the recording format,using a 2 ch ×2 head system, according to Embodiment 10. The arrowsindicate the head scanning traces. The servo is locked in the area where16-time speed replay data is recorded. Since eight units of the 16-timespeed replay data is recorded repeatedly, one of the eight units isscanned by either of the 2 ch heads. However, for the reason describedin connection with Embodiment 5, not all the 16-time speed replay datacan be reproduced by the A-channel head alone. However, by synthesiswith the 16-time speed replay data recorded by the B-channel head andpicked up the B-channel head, the replay is possible.

The processing during replay will next be described.

FIG. 55 shows a circuit for signal processing after the error correctiondecoding in the replay system according to Embodiment 10. Referencenumeral denotes 390 a replay data input terminal for input of replaydata, 392 denotes a mode signal input terminal for input of a modesignal from a system controller or the like, 394 denotes an ID analyzerfor analyzing the ID of the sync block and selecting the replay data,396 denotes an SB header analyzer for analyzing the header appended foreach sync block and selecting the replay data, 398 denotes an SB/TPconverter for converting the replayed sync block into transport packets,and 400 denotes a replay SB output terminal.

The replay operation of the signal processing circuit will next bedescribed. The replay data received at the replay data input terminal(having received error correction decoding of the SD specification), isinput to the ID analyzer 394. A signal indicating the replay mode isalso input mode input terminal 392, and then to the ID analyzer 394. Onthe basis of the mode signal, the ID analyzer 394 judges whether thenormal replay or the special replay is selected, and outputs the normalreplay data recorded in the main areas, to the next stage. If thespecial replay is selected, the data recorded in the special replayareas is output, sync block by sync block, to the next stage. In each ofthe replay mode, data for the other replay mode is discarded. Whethereach sync block is from the main areas or from the special replay areasis determined from the ID or the header appended for each sync block.

The data selected and output by the ID analyzer 394 is input to the SBheader analyzer 396. On the basis of the replay mode signal, the SBheader analyzer 396 is informed of the speed of the fast replay andoutputs the sync blocks corresponding to the speed of the fast replay.The data from the special replay areas which do not correspond to thereplay mode signal is discarded. During normal replay, the input data isoutput as is. The discrimination is made on the basis of the ID or theheader appended for each sync block.

The data output from the SB header analyzer 396 is input to the SB/TPconverter 398, which converts the sync blocks into transport packets,and output via replay SB output terminal 400.

In this way, only the data recorded in the main areas is used duringnormal replay, while only the data recorded in the special replay areasis used in the special replay at various replay speeds. Both the normalreplay and special replay at various speeds can thus be achieved.

Embodiment 11

In Embodiment 11, replay of a magnetic tape having been recorded as inEmbodiment 7 will be described. In Embodiment 7, like Embodiment 5, thelow-speed fast replay speed was set at a four-time speed, themiddle-speed fast replay speed was set at an eight-time speed and thehigh-speed fast replay speed was set at a 16-time speed. In Embodiment11, the replay at the respective fast replay speeds is performed in thesame way as in Embodiment 10.

The processing during replay will first be described. FIG. 56 is acircuit for processing after the error correction decoding in the replaysystem of Embodiment 11. In the drawing, reference numeral 402 denotes areplay data input terminal, 404 denotes an ID check circuit for checkingwhether the IDs are corrected reproduced, 406 denotes a sync paritycircuit for checking the digital data within sync block after the ID,408 denotes a replay data output terminal, and 410 denotes a flag outputterminal.

The operation of the signal processing circuit will next be described.The replay data received at the replay data input terminal 402 issupplied to the ID check circuit 404, which checks the ID of the syncblock of the replay data. If the ID is correctly reproduced, the data ofthe sync block is output via the replay data output terminal 408. Thereplay data received at the replay data input terminal is also suppliedto the sync parity check circuit 406, which checks the digital datawithin the sync block and output a flag indicating the result of thecheck, via the flag output terminal 410. If it is found, as a result ofthe check of the digital data using the sync parity that an error iscontained, the flag via the flag output terminal 410 indicates to theerror correction decoder in the next stage, that the data being outputvia the replay data output terminal 408 may contain an error. In thisway, it is possible to promptly detects input of replay data containinga burst error to the error correction decoder, and to detect erroneouscorrection at the error correction decoder.

The error correction decoder performs error correction using the cl code330 and C2 code 331 shown in FIG. 32. The processing of data output fromthe error correction decoder is similar to the processing after theerror correction decoding (FIG. 55) described in connection withEmbodiment 10.

In this way, only the data recorded in the main areas is used during thenormal replay, while only the data recorded in special replay areas isused during special replay at various replay speeds, and normal replayand special replay at various speeds can be achieved.

In Embodiment 11, the flag is output to the error correction decoder. Asan alternative, a gate circuit may be provided, and decision may be madeas to whether or not the replay data should be supplied to the errorcorrection decoder based on the flag. With such an arrangement, the datacontaining a burst error can be detected promptly.

Embodiment 12

In Embodiment 12, description is made of the format in which thetransport packets are recorded in fixed areas such as sync blocks.

FIG. 57 shows an example of data packet according to Embodiment 12. Thisdata packet format is basically identical to the format in which fivesync blocks are recorded in two transport packets according toEmbodiment 7. In the drawing, reference numeral 300 denotes a sync of async block 0 (SB0), 301 denotes a sync of a sync block 1 (SB1), 302denotes a sync of a sync block 2 (SB2), 303 denotes a sync of a syncblock 3 (SB3), and 304 denotes a sync of a sync block 4 (SB4). Referencenumeral 305 denotes ID of SB0, 306 denotes ID of SB1, 307 denotes ID ofSB2, 308 denotes ID of SB3, and 309 denotes ID of SB4. Reference numeral310 denotes a header appended to SB0, 311 denotes a header appended toSB1, 312 denotes a header appended to SB2, 313 denotes a header appendedto SB3, and 314 denotes a header appended to SB4. Reference numeral 315denotes a transport header of the transport packet A, 316 denotes dataof the transport packet A, 317 denotes a transport header B of thetransport packet B, and 318 denotes data of the transport packet B.Reference numerals 319a and 319b denote dummy areas.

Description is made of SB0 ID 305 and header 310 contain an address foridentifying the particular sync block within the five sync blocks, asignal indicating whether normal replay data or special replay data isrecorded, a signal for identifying the speed where the special replaydata is recorded, a signal for indicating the identity of data forseveral units needed since identical special replay data is recorded forseveral units and discriminating from the special replay data recordedin the succeeding several units, and a signal for identifying theassembly of the five sync blocks, for each unit of the five blocks, anda signal indicating whether the central part of the screen (picture) ofan intra-frame or intra-field. In this embodiment, address identifyingeach sync block within the group of five sync blocks and a signalindicating whether normal replay data or special replay data iscontained are recorded in ID 305, and the remainder is recorded in theheader 310 disposed after the ID, for each sync block.

SB1, SB2, SB3 and SB4 record an ID and a header, like SB0 In thisembodiment, the size of the sync block is 82 bytes (excluding the C1area), the size of each sync is 2 bytes, the size of each ID is 3 bytes,and the size of each header is one byte. The size of the transportpacket is 188 bytes. Accordingly, two transport packets (188×2=376bytes) can be recorded in the data regions of five sync blocks (78×5=300bytes). The remaining four byte may be allocated for dummy areas 819aand 819b, shown in FIG.57, two bytes each, and a predefined values maybe recorded there. In this way, two transport packets can be recorded infive sync blocks.

FIG. 58 shows a modification of the data packet format of FIG. 57. It issimilar to that of FIG. 57. But in place of the two dummy areas 819a and819b, a single dummy area 819c is provided, and four bytes of predefinedvalues may be recorded in the dummy area 319c.

In the above-described embodiment, the size of the header is one byte.By removing, at the time of recording, the byte indicating thesynchronization within the transport header, the size of the transportpacket can be reduced, and the area spared may be added to form a largerheader. Necessary signals other than those described in this embodimentmay be recorded in the area spared in that way.

In this way, an identical format may be used in the main areas and thespecial replay areas, and reproduction can be made in the form oftransport packets. It is therefore unnecessary to newly form transportpackets at the time of replay.

Embodiment 13

Embodiment 13 relates to an arrangement with which a password can berecorded together with a video program, and the recorded video programcan be replayed only upon input of a password identical to the passwordrecorded with the program. By the use of a password, the program can beprotected from unauthorized replay. The password can be recorded in thearea which is used as the dummy area in Embodiment 12.

FIG. 59 is a circuit for signal processing after the error correctiondecoding in the replay system according to Embodiment 13. In thedrawing, reference numerals 390 to 396 denote members identical to thosein FIG. 55. Reference numeral 420 denotes an SB/TP converter forconverting the sync blocks into transport packets, and separating thepassword from the replay data. Reference numeral 422 denotes a passwordinput terminal for input of a password by a user, and 424 denotes apassword check circuit for comparing the password input by the user witthe password from the replay data. Reference numeral 426 denotes amessage signal generator for generating a video signal for displaying amessage to the user (viewer) indicating that the recorded program isaccompanied with a password, and cannot be replayed unless a correctpassword is input. The message signal is selected and output when therecorded program being reproduced from the tape is accompanied with apassword, and no password is input by the user (viewer) at the time ofreplay, or the password input by the user (viewer) at the time of repaydoes not match the recorded password. Reference numeral 430 denotes areplay SB output terminal.

FIG. 60A and FIG. 60B show the configuration of the password areaaccording to Embodiment 13. In FIG. 60A, reference numeral 440 denotes adummy area 319a or dummy area 319b in FIG. 57. Subareas 441, 442, 443and 444, each having four bits, are formed by dividing the dummy area440 into four, and are called password subareas A, B, C and D.

In FIG. 60B, reference numeral 450 denotes a dummy area 319c in FIG. 58.Subareas 451, 452, 453 and 454, each having eight bits, are formed bydividing the dummy area 440 into four, and are called password subareasE, F, G and H.

Since the password subareas 441 to 444 each have four bits, eachpassword subarea can express a number of 0 to 9, so that password offour digits can be recorded. Since the password subareas 451 to 454 eachhas one byte, each subarea can record an English alphabetic letter, or anumber, so a password of four digits, each digit being either a numberor an English alphabetic letter, can be recorded. The password can beset by the user at the time of recording a program, and recorded. Whenthe user does not set the password, a predefined value, e.g., of "1" forall the bits, may be recorded to indicate that no password has been set.

Now the description is made of replay operation. The replay sync blocksare input to the SB/TP converter 420, where five sync blocks aresynthesized, and two transport packets are extracted from the five syncblocks. The data (of four digits) recorded at the password area isextracted, and supplied to the password check circuit 424, while thetransport packet is supplied to the selector 428. The data from thepassword area is checked by the password check circuit 424. If the datais of a predefined value, i.e., if the data consists of bits which areall "1" in the example under consideration, then the program is treatedas being not protected by a password. If the data from the password areais not of the predefined value, and if a password is input by the user(viewer), which is supplied via the password input terminal 422 to thepassword check circuit 424, the input password is compared with therecorded password. If they match, the processing will be the same as inthe case where the password is not recorded, and the selector 428 ismade to select the transport packets forming the replay data. If thepasswords do not match, or if no password is input by the user (and ifthe recorded program is accompanied with a password) the selector 428 ismade to select the signal from the message signal generator 426, and amessage is displayed, indicating that the program is protected by aprogram and cannot be replayed unless a correct password is input. Itmay alternatively be so arranged that when no password is input whilethe recorded program is protected by a password a message prompting theuser to input a password is displayed, and when a wrong password isinput a message indicating the input password is wrong, and a correctpassword should be input is displayed.

When the program is protected by a password, and a correct password isnot input, display of the program is inhibited. This is achieved by theoperation of the selector 428, which does not select the transportpackets forming the replay data. Additionally (or alternatively), thetape transport and head scanning may also be stopped, unless or until acorrect password is input.

With the configuration and operation described above, it is possible toprotect the program from being seen by an unauthorized user.

Embodiment 14

In Embodiment 10, replay is performed at a speed set by Embodiment 5. InEmbodiment 14, replay is performed from special replay areas for aspecific speed, at a speed lower than the specific speed.

FIG. 61 shows head scanning traces of the rotary head during six-timespeed replay of eight-time speed replay data in a recording format ofFIG. 29, using a 1 ch×2 head system, according to Embodiment 14. Thearrows indicate the head scanning traces. The special replay data forthe six-time speed replay is obtained by reproducing the eight-timespeed replay data, four units of which are repeatedly recorded in theeight-time speed replay areas. When reproducing at a six-time speed fromthe eight-time speed replay areas, the servo is locked at the eight-timespeed replay areas. By this method, identical special replay data may bereproduced twice. In that case, one of them is discarded, to achievereplay at a six-time speed.

FIG. 62 shows head scanning traces of the rotary head during six-timespeed replay of eight-time speed replay data in a recording format ofFIG. 29, using a 2 ch×1 head system, according to Embodiment 14. Thearrows indicate the head scanning traces. The special replay data forthe six-time speed replay is obtained by reproducing the eight-timespeed replay data, four units of which are repeatedly recorded in theeight-time speed replay areas. When reproducing at a six-time speed fromthe eight-time speed replay areas, the servo is locked at the eight-timespeed replay areas. By this method, identical special replay data may bereproduced twice. In that case, one of them is discarded, to achievereplay at a six-time speed.

FIG. 63 shows head scanning traces of the rotary head during six-timespeed replay of eight-time speed replay data in a recording format ofFIG. 29, using a 2 ch ×2 head system, according to Embodiment 14. Thearrows indicate the head scanning traces. The special replay data forthe six-time speed replay is obtained by reproducing the eight-timespeed replay data, four units of which are repeatedly recorded in theeight-time speed replay areas. When reproducing at a six-time speed fromthe eight-time speed replay areas, the servo is locked at the eight-timespeed replay areas. By this method, identical special replay data may bereproduced twice. In that case, one of them is discarded, to achievereplay at a six-time speed.

In Embodiment 14, description is made of the cases where the replay fromthe eight-time speed areas is conducted at a six-time speed. But theinventive concept described above can be applied to situations wherereplay from special replay areas for a set replay speed is conducted ata replay speed lower than the set speed.

Embodiment 15

In Embodiment 15, replay is made from special replay areas for aspecific replay speed, at a replay speed higher than the specific replayspeed. Description is made for the case in which replay is effected fromthe areas for four-time speed in Embodiment 5, at 12-time speed.

FIG. 64 shows head scanning traces of the rotary head during twelve-timespeed replay of four-time speed replay data in a recording format ofFIG. 29, using a 1 ch×2 head system, according to Embodiment 15. Thearrows indicate the head scanning traces. The special replay data forthe twelve-time speed replay is obtained by reproducing the four-timespeed replay data, two units of which are repeatedly recorded in thefour-time speed replay areas. When reproducing at a twelve-time speedfrom the four-time speed replay areas, the servo is locked at thefour-time speed replay areas.

FIG. 65 shows head scanning traces of the rotary head during twelve-timespeed replay of four-time speed replay data in a recording format ofFIG. 29, using a 2 ch×1 head system, according to Embodiment 15. Thearrows indicate the head scanning traces. The special replay data forthe twelve-time speed replay is obtained by reproducing the four-timespeed replay data, two units of which are repeatedly recorded in thefour-time speed replay areas. When reproducing at a twelve-time speedfrom the four-time speed replay areas, the servo is locked at thefour-time speed replay areas.

FIG. 66 shows head scanning traces of the rotary head during twelve-timespeed replay of four-time speed replay data in a recording format ofFIG. 29, using a 2 ch ×2 head system, according to Embodiment 15. Thearrows indicate the head scanning traces. The special replay data forthe twelve-time speed replay is obtained by reproducing the four-timespeed replay data, two units of which are repeatedly recorded in thefour-time speed replay areas. When reproducing at a twelve-time speedfrom the four-time speed replay areas, the servo is locked at thefour-time speed replay areas.

FIG. 67A and FIG. 67B are used to explain the fast replay according toEmbodiment 15. FIG. 67A shows the configuration of the recording areasof the four-time speed replay data. FIG. 67B shows the positions on thescreen. In each of the cases shown in FIG. 64 to FIG. 66, it isnecessary to record the data in the four-time speed special replay areasin the form shown in FIG. 67A and FIG. 67B. In the drawing, referencenumeral 242 denotes a special replay area for four-time speed, recordedby an A-channel head, 244 denotes a special replay area for four-timespeed, recorded by a B-channel head, 460 denotes a one intra-frame orone intra-field screen as a whole, and 462 denotes a central part of theone intra-frame or one intra-field screen.

Of the data recorded in the special replay area 242 for four-time speed,recorded by the A-channel head, the central part (in the embodimentunder consideration, the servo is assumed to be locked at the centralpart of each special replay area) is used to record the data of thecentral part 462 of the screen of one intra-frame or intra-fieldpicture. This data is part of the four-time speed data, and noadditional four-time speed areas are used. It is sufficient if thefour-time speed special replay areas 242, recorded by the A-channelhead, is recorded at an interval of a predefined number of tracks. Inthis embodiment, since twelve-time speed replay is effected, theinterval consists of six units, each unit consisting of four tracks. Ofthe special replay areas 242 recorded by the A-channel head, the areasother than the areas where the data of the central part 462 of thescreen (whole picture) of one intra-frame or intra-field picture, andthe four-time special replay areas 244 recorded by the B-channel headare used to record the data other than the data of the central part 462of the screen of one intra-frame or intra-field picture, that is thedata of the screen 460 of one intra-frame or intra-field picture minusthe data of the central part 462 of the screen of the one intra-frame orintra-field picture. By replaying the signal for the central part of thescreen, the special replay with a high picture quality and with frequentrefreshing can be obtained.

In Embodiment 15, description is made of the cases where the replay fromthe four-time speed areas is conducted at a twelve-time speed. But theinventive concept described above can be applied to situations wherereplay from special replay areas for a set replay speed, in a format inwhich the special replay areas for the set replay speed is collectivelydisposed, is conducted at a replay speed higher than the set speed.

In Embodiment 15, description is made of the cases where the centralpart of the screen of an intra-frame or intra-field image is recorded inpart of the special replay area recorded by an A-channel head. Theinvention is not limited to this particular arrangement. The centralpart of the screen of an intra-frame or intra-field image may berecorded in such part of the special replay area for a set replay speedfrom which data can be reproduced at a speed higher than the set replayspeed, in the recording format in which the special replay data isrecorded at one location where the special replay area for the setreplay speeds are concentrated as shown in FIG. 29.

Embodiment 16

In the following Embodiments 16 to 19, description is made of variousdevices for removing the effects of fluctuation in the head position toensure reproduction of replay data at a high speed.

As an example, it is assumed, according to the basic specification ofthe prototype consumer digital VTR, each track on the tape correspondsto 186 sync blocks (SBs), the difference between the starting positionsof the adjacent track in the track longitudinal direction is d syncblocks (d=0.35 SB), and the track width and the head width areidentical. Embodiment 16 is described on the above assumption.

FIG. 68 is a block diagram showing a recording system of a digital VTRaccording to Embodiment 16. In the drawing, reference numeral 470denotes an input terminal for an ATV signal bit stream, 472 denotes avariable-length decoder, 474 denotes a counter, 476 denotes a dataextractor, 478 denotes an EOB (end of block) appending circuit, and 480denotes a sync signal generator. Reference numeral 482 denotes a syncblock generator, which appends the sync bytes to the bit stream, on thebasis of the sync signal from the sync signal generator 480, to formsync blocks to be recorded in the main areas on the tracks, and formsfast replay sync blocks on the basis of the fast replay signal from theEOB appending circuit 478, to thereby form a signal to be recorded inthe predefined sync blocks. Reference numeral 484 denotes a recordingsignal processor for performing recording signal processing such asrecording modulation and recording amplification, 70 denotes heads oftwo different azimuths, and 10 denotes a magnetic tape.

The recording operation by the above recording system will next bedescribed in detail. MPEG2 bit stream is input via the input terminal470, and supplied to the sync block generator 482, where sync bytes areappended, on the basis of the sync signal from the sync signal generator480, to form sync blocks. The bit stream received at the input terminal470 is also supplied to the variable-length decoder 472, where thesyntax of the MPEG2 bit stream is analyzed, and intra-images areextracted, and timing signals are generated by the counter 474, and thelow-frequency components of all the blocks of the intra-images areextracted at the data extractor, and EOBs are appended at the EOBappending circuit 478, to form fast replay data, which is output to thesync block generator 482. On the basis of the sync signal from the syncsignal generator 480, the sync block generator 482 appends sync bytes tothe fast replay signal from the EOB appending circuit 478, to form thesync blocks for fast replay, and forms a recording signal to be recordedin the predefined sync blocks.

The recording signal formed of the respective sync blocks from the syncblock generator 482 is supplied to the recording signal processor 484,where various recording signal processing, such as digital recordingmodulation, and recording amplification, are applied, and then suppliedto the heads 70 of two different azimuths, and recorded on the magnetictape 10.

Next, description is made of the disposition on the tracks for recordingfast replay sync blocks which are fast replay data.

FIG. 69 shows a scanning trace of a rotary head on the tracks duringfast replay. The drawing shows the case where the replay speed isfive-time speed, i.e., the speed multiplier m is five, and the length ofthe tracks in terms of the number of the sync blocks sync block is 186SBs, and the difference d between the starting positions of the adjacenttracks A and B, in the track longitudinal direction is 0.35 SB. Therelationship between the difference D between crossing positions in thetrack longitudinal direction, and the length Te of the areas of thetrack from which reproduction is possible is illustrated. If the tapespeed m is an integer-multiple speed, and the phase lock is controlled,the head scanning is in synchronism with the tracks of the identicalazimuth, and the positions of the data which is reproduced are fixed.

Referring to FIG. 69, if it is assumed that such part of the replaysignal whose output level is -6 dB or greater is reproduced, the head Acan reproduce data from the hatched regions. If the track width and thehead width are identical, the different D between the crossing positionsof the head A in the track longitudinal direction is

    D=Te+Tu, where Te=Tu,

and the total length of the regions from which reproduction is possibleis

    Te=(S-(m-1)×d}/(m-1)

FIG. 70 shows a scanning trace of a rotary head during replay at 56-timespeed. FIG. 71A to FIG. 71C are for explaining the position fluctuationof the rotary head scanning trace. FIG. 71A shows the scanning trace bywhich three sync blocks can be reproduced, while FIG. 71B and FIG. 71Cshow the scanning traces shifted forward and backward. The regions fromwhich the reproduction of the signal is ensured during 56-time speedreplay is hatched regions. Each of the regions from which reproductionis possible, as determined by the above-recited equation, amounts to:

    Te=(S-SS×d)/55=3.0SB

The maximum number n (n being an integer) of consecutive sync blockswhich can always be reproduced from the above region Te=3.0 SB, in otherwords, minimum number n (n being an integer) of consecutive sync blockswithin the above region Te=3.0 SB from which reproduction of data isensured, is n=2 SB. This is because the limits of the region from whichreproduction is possible do not necessarily coincide with the boundariesof the sync blocks, as shown in FIG. 71A to FIG. 71C. For instance, thesync block j2 is read in the case of FIG. 71A, but not in the case ofFIG. 71B. The sync block j4 is read in the case of FIG. 71A, but not inthe case of FIG. 71C. Accordingly, the maximum number of the consecutivesync blocks, within the region from which reproduction is possible, fromwhich reproduction is possible without fail is 2 SB if Te=3 SBs. If Teis not an integer, such maximum number is n=t-1 SB, where t is a maximuminteger which does not exceeds Te. It is seen from the above that, inthe case of 56-time speed replay, fast replay sync blocks should berecorded in the areas 1 to 3 in FIG. 70.

When, however, fast replay is conducted using a rotary drum, theposition at which the head crosses the respective tracks may be shiftedbecause of the fluctuation in the head scanning trace due to the tapespeed fluctuation, the drum rotational speed fluctuation, and like. Insuch a case, it is necessary to read the data of 2 SBs for fast replay,without fail. If the maximum value of shift, from the referenceposition, of the actual position at which the head crosses a specifictrack during fast replay at a certain speed is w sync blocks (havingrounded up to the next integer, i.e., the actual shift being not morethan w sync blocks, but more than (w-1) sync blocks), the range of shiftis ±w SB in the track longitudinal direction from the reference positionwhich is attained when the phase is locked.

FIG. 72 shows disposition of the fast data according to Embodiment 16.It is assumed that the shift at 56-time speed is w=4 SB. The regionwithin which the sync blocks may be scanned because of the shift extend(n+2×w)=10 SB. Accordingly, if the data for 2 SB is designated by D1 andD2, the data D1 and data D2 are repeatedly and cyclically recorded forthe range of (n+2×w) sync blocks. FIG. 73 shows an example ofdisposition of the fast replay data on a track according to Embodiment16. High-speed replay data is sequentially (in the ascending order ofsuffix i to D) and repeatedly (or cyclically) recorded over 10 syncblocks, numbered X, X+1, . . . X+9, centered on the reference positionof the region where replay is possible by the head crossing a specifictrack.

With this arrangement, it is possible to ensure reproduction of therecorded sync block data D1 and D2 of 2 SB for fast replay during fastreplay at a certain speed, even when the position at which the headcrosses the specific track is shifted.

FIG. 74 is a block diagram showing a replay system of a digital VTR ofEmbodiment 16. In the drawing, reference numerals 70 and 10 denotemembers identical to those in the recording system shown in FIG. 68.Reference numeral 490 denotes a replay signal processor for performingreplay signal processings, such as waveform equalization, signaldetection and recording demodulation, 492 denotes a replay dataseparator for separating the normal replay data and the fast replay datain the replay signal, 494 denotes a selector, 496 denotes a replay modesignal generator for generating a signal indicating the replay mode, and498 denotes an output terminal.

During replay, the replay signal replayed by the head 70 from themagnetic tape 10 is supplied to the replay signal processor 490, wherereplay signal processings, such as waveform equalization, signaldetection, and recording demodulation, are applied. The replay signal isthen supplied to the replay signal separator 492, where the signalreplayed from the tracks is separated into the bit stream (g) for normalreplay data, and the sync block data for fast replay, which are thensupplied to the selector 494. On the basis of the signal indicating thereplay mode, from the replay mode signal generator 496, the selector 494selects the normal replay data (g) during normal replay, and the fastreplay data during fast replay, and the selected data is output via theoutput terminal 498, and sent to an MPEG2 decoder provided outside ofthe digital VTR.

In the manner described above, by recording n pieces of data Di (i=1, 2. . . n) each of which can be recorded in one sync block sequentiallyand repeatedly in (n+2×w) consecutive sync blocks from which data isreproduced at m-time speed, it is ensured to read fast replay data evenwhen the position of the head scanning trace fluctuates, because of thetape transport speed fluctuation, or the drum rotary speed fluctuation,and fast replay pictures with a good quality can be obtained, and muchof the data for fast replay can be recorded and replayed.

Embodiment 17

In Embodiment 16, sync block data for fast replay is recorded inpredefined positions on predefined tracks which are scanned duringm-time speed replay. It is also possible to repeatedly record the fastreplay data so that the fast replay data can be can be read regardlessof the identical-azimuth track at which (at whose end) the rotary headbegins scanning. In that case, the pull-in of the servo system is quickand the fast replay image can be obtained instantly.

FIG. 75 shows the positional relationship between the scanning tracesand the fast replay data according to Embodiment 17. Identical syncblock positions on various identical-azimuth tracks are scanned, fromrespective starting points. To enable m-time speed replay, identicalsync block data for fast replay is repeatedly recorded over (n+2×w)consecutive sync blocks at identical position on each of at least mconsecutive identical-azimuth tracks, as shown, by way of example, inFIG. 76. In this way, regardless of the track (of the identical azimuth)at which the fast replay is started, the replay data can be obtained.

In the manner described above, by repeatedly recording m-time speedsignal is recorded in (n+2×w) consecutive sync blocks at identicalpositions on m consecutive identical-azimuth tracks, reading of the fastreplay data is ensured in the event of fluctuation in the head scanningtraces due to tape speed fluctuation and drum rotary speed fluctuation,and reproduction of good quality pictures is ensured, and much fastreplay data can be recorded and replayed.

Embodiment 18

Embodiment 18 relates to a bit stream recording and replay devicecapable of fast replay, with a different example of disposition, ontracks, of fast replay sync block forming fast replay data.

FIG. 77 to FIG. 79 show rotary head scanning traces during 56-time speedreplay according to Embodiment 18. FIG. 77 to FIG. 79 show examples of56-time speed replay, with different phase control positions anddifferent head traces. Replay signals are picked up from the hatchedportions. For instance, in FIG. 77, the fourth to sixth sync blocksi.e., from the beginning of the fourth sync block to the end of sixthsync block, or 4.0-th to 7.0-th sync blocks are read. Similarly, in FIG.78, the 4.7-th to 7.7-th sync blocks are read, and in FIG. 79, the5.7-th to 8.7-th sync blocks are read.

To ensure reading of replay data at fast replay, at whichever phase thehead traces is achieved, it is so arranged that, even when the fastreplay signal is not obtained from one track during fast replay, readingof the signal from the next identical-azimuth track is ensured. That is,even when the head trace position is shifted due to phase fluctuation,the recorded sync block data for fast replay can be obtained from thetotal of one track and a next identical-azimuth track.

FIG. 80 shows the positional relationship between the scanning trace andthe fast replay data according to Embodiment 18. It shows the positionsof the regions Te in two identical-azimuth tracks A1 and A2 from whichreproduction is possible during fast replay. In FIG. 80, if thereproduction is possible from the portions where the level of the outputreplay signal is greater than -6 dB, the signals are reproduced from thehatched regions in the tracks A1 and A2. If the track width and the headwidth are identical, the length Tu which is the difference between theupper end and lower ends of the regions on the tracks A1 and A2 is givenby:

    Tu={S-(m-1)×d}/(m-1)

The position of the sync block in track A2 is 2 d sync blocks higherthan the position in track A1.

FIG. 81A and FIG. 81B show the fluctuation in the position of the rotaryhead scanning trace according to Embodiment 18. (A) shows the scanningtrace by which 3 sync blocks can be reproduced, and (B) shows thescanning trace followed when the position is varied. To ensurereproduction of fast replay sync block data from the twoidentical-azimuth tracks A1 and A2 during fast replay, even when headscanning phase is changed in the two identical-azimuth tracks A1 and A2,sync block data of a length of not less than (Te+Tu) sync blocks isrepeatedly recorded on track A1, from the starting point of the regionwhere the fast replay sync block is recorded, toward the tail end of thetrack.

For instance, when fast replay is performed at 56-time speed, themaximum number of sync blocks which can always be consecutivelyreproduced from the track region on the tape is n=2, and the length ofthe region from which the replay signal can be obtained is Te=3 SB. Iffast replay sync block data D1 and D2 is repeatedly record over 6 SB inthe direction of from sync block 1 to sync block 6, in FIG. 81A and FIG.81B, the fast replay data can be read, even if the phase is shifted inthe track longitudinal direction, toward the tail end of the track. Intrack A2 also, if fast replay data is repeatedly recorded over (Tu+Te+2d) from the tail end of the region from which the reproduction ispossible toward the head end of the track, as shown in FIG. 80, the fastreplay data D1, D2 can be read from the track A2, even if the phase isshifted in the track longitudinal direction, toward the head end of thetrack.

Let us now consider the case where the sync block data D1, D2 is to beobtained from the track A2 only, or the case where the sync block D1 isobtained from track A1, and D2 is obtained from track A2. In the casewhere the sync block data D1, D2 is to be obtained from track A2, thesync block data should be recorded up to such a position that sync blockdata D1 can be read from track A1 and sync block data D1, D2 can be readfrom the track A2. FIG. 82 is a schematic diagram showing the positionat which sync block data D1 can be read from track A1 and sync blockdata D1, D2 can be read from the track A2. The fast replay signal D1, D2should be disposed in the sync blocks in the hatched region of from the(Tu+2 d+1)-th sync block to (D+2 d+1) on the track A2.

In the case where sync block data D1 is obtained from the track A1, andthe sync block data D2 is obtained from the track A2, the sync blockdata should be recorded to such a position that the sync block data D1,D2 can be read from the track A1 and the sync block data D2 can be readfrom the track A2. FIG. 83 shows the schematic diagram showing theposition at which the sync block data D1, D2 can be read from the trackA1 and the sync block data D2 can be read from the track A2. The fastreplay signal D2 should be disposed in the sync blocks in the hatchedregion of from (Tu+2 d+2)-th sync block to (D+2 d+2) sync block on thetrack A2 in the drawing.

From the above it is seen that, when fast replay is performed at 56-timespeed for instance, the maximum number of sync blocks which can alwaysbe reproduced consecutively is n=2 SB, the length of the region fromwhich the replay signal can be obtained is Te=3 SB, and where the syncblock data D1 is read from the track A1, and the sync block data D1, D2is read from the track A2, the fast replay signal D1, D2 are disposed inthe sixth and seventh sync blocks in the region on the track A2 fromwhich reproduction is possible, as shown in FIG. 84. When the sync blockdata D1, D2 is read from the track A1 and the sync block data D2 is readfrom the track A2, the fast replay signal D2 is disposed in the seventhsync block as shown in FIG. 85. In this case, the fast replay speedsignal is repeatedly recorded in the respective identical-azimuthtracks, and, in doing so, the two pieces of sync block data D1, D2 aresequentially (in the ascending order of the suffix i to D) repeatedlyrecorded in seven consecutive sync blocks at identical position on therespective tracks, and the data are so disposed that the seventh data ofthe track identical to the second data (D2 in the example of FIG. 85) ofthe seven pieces of fast replay data recorded in the identical syncblock position on the immediately preceding identical-azimuth track, andthe disposition in the fast replay regions on the tracks is as shown inFIG. 86.

FIG. 87 shows the length of the sync blocks for the fast replay datawhere the fast replay is performed at m-time speed, the maximum numberof the sync blocks which can always be reproduced consecutively from theregion on the track of the tape is n, and the length of region fromwhich the reproduction signal can be obtained is Te, the differencebetween the head crossing positions in the track longitudinal directionis D=Te+Tu, and n pieces of sync block data D1, D2 . . . Dn areconsecutively recorded. When the minimum integer which is not smallerthan (Tu+2 d) corresponds to L (here, Tu=D-Te), n sync block data aresequentially (in the ascending order of the suffix i to D) repeatedlyrecorded in (L+n+1) consecutive sync blocks at identical positions onthe tracks and the data are so disposed that the (L+n+1)-th data in thetrack is identical to the n-th data (Dn in the example shown in FIG. 87)of the fast replay data recorded in the identical sync block position onthe immediately preceding identical-azimuth track, and recorded on atleast m identical-azimuth track. With such an arrangement, the readingof the fast replay signal is ensured even if the phase is varied.

Disposing the data such that the (L+n+1)-th data on the track to beidentical to the n-th data of the fast replay data recorded at the samesync block position on the immediately preceding identical-azimuth trackmeans recording the data Di to satisfy the relationship

    e2=mod {e1+n-mod(n+L+1, n)}, n!

where mod (a, b) expresses the remainder of numeral a divided by numeralb, and the suffixes of D recorded first on tracks A1 and A2 are e1 ande2 (integers not less than 1 and not more than n).

When the fast replay signal for m-time speed is recorded in the abovemanner, n pieces of data Di (i =1, 2 . . . n) each of which can berecorded in one sync block are sequentially (in the ascending order ofthe suffix i to D) and repeatedly recorded in (L+n+1) consecutive syncblocks, and the data are so disposed that the (L+n+1)-th data on thetrack is identical to the n-th data of the fast replay data recorded atthe same sync block position on the immediately precedingidentical-azimuth track. Accordingly, reading of fast replay data isensured even when the head trace phase is varied due to variation in thehead scanning traces, and fast replay images with a good quality can beobtained, and much fast replay data can be reproduced.

Embodiment 19

In Embodiment 18, fast replay data of the maximum number n of syncblocks which can always be reproduced consecutively from the region ofthe track on the tape, during m-time speed replay of fast replay data,is repeatedly recorded in a necessary number of sync blocks, (L n+1).The number p of the fast replay data may be less than n (p being anatural number), and the number of the regions for the fast replay maybe more than (L+n+1).

FIG. 88 is a schematic view showing the data on the respective tracks inthe case where the data of the maximum number n of sync blocks which canalways be reproduced consecutively from the region of the track on thetape during the fast replay at 30-time speed is recorded as the fastreplay data. At 30-time speed, the maximum number of sync blocks whichcan always be reproduced consecutively from the region of the track onthe tape is five, and the length of the region from which the replaysignal can be obtained is Te=6 SB, and the length of the sync blocks ofthe fast replay data where the five sync block data D1, D2 . . . D5 areconsecutively recorded is (L+n+1)=13 sync blocks which are consecutiveat identical positions on the tracks. (Here, L is again a minimuminteger not smaller than (Tu+2 d).) The data are sequentially (in theascending order of the suffix i to D) and repeatedly recorded, and thedata are so disposed that the 13-th data on the track is identical tothe fifth data of the fast replay data recorded at the identical syncblock position on the immediately preceding identical-azimuth track. Inthis way, reading of the fast replay signal is ensured even if the phasefluctuates.

FIG. 89 shows disposition of the data in the fast replay region in thecase where the fast replay data is for the fast replay at 30-time speedand is formed of p=2 sync blocks. For conducting 30-time speed replay,the length of the sync blocks of the fast replay data used for recordingthe two sync block data D1, D2 consecutively is (L+p+1)=10 sync blocksand these 10 sync blocks are consecutive at the same position on thetrack. (Here, L is again a minimum integer not smaller than (Tu+2 d).)The data are sequentially (in the ascending order of the suffix i to D)and repeatedly recorded, and the data are so disposed that the 10-thdata of the track is identical to the p=2nd data of the fast replay datarecorded at the same sync block position on the immediately precedingidentical-azimuth track. In this way, even when the phase fluctuates thereading of the fast replay signal is ensured. FIG. 90 shows an exampleof disposition of fast replay data. Specifically, it shows thedisposition of data in the fast replay region for the case where thedata for the 30-time speed replay is formed of p=2 sync blocks.

Since the length of the region for the fast replay data is 10 syncblocks, the 56-time speed replay according to Embodiment 18, and thefast replay at a speed with which the maximum number of sync blockswhich can always be reproduced consecutively is not less than 2 and notmore than 6 may be performed, and yet the reading of the fast replaysignal is ensured even if the phase fluctuates. FIG. 91 shows scanningtraces in 56-time speed replay. In this case, the length of sync blocksnecessary for always reading two data is 7 as was explained inconnection with Embodiment 18, and with the arrangement of FIG. 90,reading is ensured regardless of the phase. FIG. 92 shows disposition ofthe fast replay data and head traces during 44-time speed replay. Themaximum number of sync blocks which can always be reproducedconsecutively is 3, and Te=Tu=4.0 SB, so (L+p+1) is 8 SB. With thedisposition of FIG. 90, too, reading is ensured at 44-time speedregardless of the phase. Accordingly, the example of FIG. 90 enablesfast replay from 30-time speed to 56-time speed.

Disposing the data such that the (L+p+1)-th data on the track isidentical to the p-th data of the fast replay data recorded at the samesync block position on the immediately preceding identical-azimuth trackmeans recording data Di in such a manner as to satisfy the relationship:

    e2=mod {e1+p-mod(p+L+1, p)}, p!

where mod (a, b) expresses the remainder of a divided by b; and

e1, e2 (integers not less than 1 and not more than n) are suffixes todata D which are recorded first on the tracks A1 and A2, respectively.

In the manner described above, in recording the m-time speed fast replaysignal on the tracks, p pieces of data Di (i=1, 2 . . . p) each of whichcan be recorded in one sync block are sequentially (in the ascendingorder of the suffix i to D) and repeatedly recorded in the (L+p+1)consecutive sync blocks at the same position on the identical-azimuthtracks, and the data are so disposed that the (L+p+1)-th data on thetrack is identical to the pth data of the fast replay data recorded atthe identical sync block position on the immediately precedingidentical-azimuth track, and the data is recorded on at least midentical-azimuth tracks. With such an arrangement, even when the headscanning traces fluctuates or the head trace phase is shifted, readingof the fast replay data is ensured, and fast replay image of a goodquality is obtained, and much fast replay data can be recorded andreplayed.

What is claimed is:
 1. A digital VTR for recording data having digitalvideo and audio signals, with error correction codes respectivelyappended in the recording and vertical directions, in respectivepredetermined areas on oblique tracks of a magnetic recording tape in apredetermined track format, and replaying from the areas, said VTRcomprising:data separating means for extracting data of intra encodedblocks in the form of intra-frame or intra-field blocks from theintra-frame or intra-field encoded, or inter-frame or inter-fieldencoded digital video signal, and the digital audio signal, contained inan input bit stream; first error correction code appending means forappending error correction code to the data of the intra-encoded blocksextracted by said data separating means; synthesizing means forcombining, in a predetermined format, said input bit stream and saidintra-encoded blocks appended with error correction code; second errorcorrection code appending means for appending error correction code tothe combined data from said synthesizing means; and recording means forrecording the data resulting from said second error correction codeappending means in the recording areas allocated in the magneticrecording tape to special replay data.
 2. The digital VTR as set forthin claim 1, wherein said recording means disposes the special replaydata recording areas in such recording areas that by scanning themagnetic recording tape once with a rotary head at a predeterminedreplay speed during replay of the special replay data, said errorcorrection code can be reconstructed.
 3. The digital VTR as set forth inclaim 1, wherein said recording means disposes the special replay datarecorded on the magnetic recording tape, taking error correction blockfor the respective replay speed as a unit, in recording areasconcentrated on oblique tracks of the magnetic recording tape.
 4. Thedigital VTR as set forth in any one of claim 1, wherein said errorcorrection code appending means appends, to said special replay data,error correction code set to have a minimum distance identical to thatof error correction code appended to the digital video or audio signal.5. The digital VTR as set forth in any of claim 1, wherein said errorcorrection code appending means appends, to said intra-encoded block,error correction code having identical magnitude for each of the replayspeeds.
 6. The digital VTR as set forth in claim 1, wherein saidrecording means disposes the error correction code in such recordingareas that by scanning the magnetic recording tape once with a rotaryhead at a predetermined replay speed during replay of the special replaydata, said error correction code can be reconstructed, saidpredetermined replay speed being either of the values corresponding topositive and negative tape transport speeds having the same absolutevalue.
 7. A system for storing digital video and audio signals in apredetermined track format on video tape, the video signals includingmain video data corresponding to image data for display during normalplay-back mode and special replay data corresponding to image data fordisplay during a special play-back mode, said system comprising:an inputunit for receiving a bit stream of encoded video and audio signals to bestored on video tape for later replay; an intra-encoded block detectorfor detecting and separating intra-encoded data to be used as specialreplay data from the received bit stream of encoded video and audiosignals; a first error correction encoder for appending error correctioncodes to the separated intra-encoded data; a synthesizer for combiningthe bit stream of encoded video and audio signals with the result ofsaid first error correction encoder to produce a recording bit steamhaving a predetermined track format; a second error correction encoderfor appending error correction codes to the synthesized recording bitstream; and a recorder for recording the resulting data from said seconderror correction encoder on the video tape.
 8. A system for storingdigital video and audio data on video tape as defined in claim 7,wherein the first error correction codes appended by said first errorcorrection encoder are appended in the vertical direction relative tothe intra-encoded data.
 9. A system for storing digital video and audiodata on video tape as defined in claim 7, wherein said second errorcorrection encoder appends first check codes to main video and specialreplay data in the recording direction and appends second check codes inthe vertical direction.
 10. A system for storing digital video and audiodata on video tape as defined in claim 7, wherein the tracks are eachcomprised of a plurality of sync blocks, the sync blocks each includinga header indicating the replay speed for which corresponding recordedspecial replay data is intended.
 11. A system for storing digital videoand audio data on video tape as defined in claim 7, wherein units ofspecial replay data are repeated in multiple tracks so as to be read atdifferent replay speeds.
 12. A method for storing digital video andaudio signals in a predetermined track format on video tape, the videosignals including main video data corresponding to image data fordisplay during normal mode and special replay data corresponding toimage data for display during a special play-back mode, said methodcomprising the steps of:receiving a bit steam comprised of encoded videoand audio signals to be stored on video tape for later replay; detectingand separating intra-encoded data for use as special replay data fromthe received bit steam of encoded video and audio signals; appendingfirst error correction codes to the separated intra-encoded data;combining the bit stream of encoded video and audio signals with theresult of said step of appending first error correction codes to producea recording bit stream having a predetermined track format; appendingsecond error correction codes to the recording bit steam; and recordingthe result of said step of appending second error correction codes onthe video tape.
 13. The method of claim 12, wherein the first errorcorrection codes appended in said step of appending first errorcorrection codes are appended in the vertical direction relative to theintra-encoded data.
 14. The method of claim 12, wherein said step ofappending second error correction codes appends first check codes tomain video and special replay data in the recording direction andappends second check codes in the vertical direction.
 15. The method ofclaim 12, wherein the tracks each include a plurality of sync blocks,the sync blocks each including a header indicating the replay speed forwhich recorded special replay data is intended.
 16. The method of claim12, wherein units of special replay data are repeated in multiple tracksso as to be read at different replay speeds.
 17. The method of claim 12,wherein the special replay data is disposed in such recording areas thaterror correction codes can be reconstructed by scanning the video tapeonce with a rotary head at a predetermined replay speed during specialplay-back mode.
 18. The method of claim 17, wherein the predeterminedspeed is either positive or negative tape transport speeds having thesame absolute value.
 19. The method of claim 12, wherein the specialreplay data is recorded in areas concentrated on oblique tracks of thevideo tape.
 20. The method of claim 12, wherein the error correctioncodes appended in said step of appending first error correction codeshave identical magnitude for each of a plurality of play-back speeds.21. The method of claim 12, wherein the error correction codes appendedin said step of appending first error correction codes have a minimumdistance identical to that of error correction codes appended to encodedvideo or audio signals.
 22. A digitally recorded tape having digitalvideo and audio signals stored thereon by a digital video tape recorderin a specific track format for later play-back by a video tape player,the track formatted data stored on said tape including:main video datacorresponding to image data for display during normal play-back; specialplay-back data corresponding to image data for display during a specialplay-back mode, said special play-back data including intra-encoded dataextracted from the original bit stream of encoded video and audiosignals and first error correction codes appended to the separatedintra-encoded data, the first error correction codes causing the videotape player to perform vertical error correction of the specialplay-back data during the special play-back mode; and second errorcorrection codes appended to a synthesized bit stream having apredetermined format, the synthesized bit stream including a combinationof the original bit stream of encoded video and audio signals and theintra-encoded data with first error correction codes, the second errorcorrection codes causing the video tape player to perform horizontalerror correction of the main and special play-back data and verticalerror correction of the main video data.